Combined human joints. Human joints anatomy

Classification of joints can be carried out according to the following principles: 1) by the number of articular surfaces, 2) by the shape of the articular surfaces and 3) by function.

Based on the number of articular surfaces, they are distinguished:
1. Simple joint(art. simplex), having only 2 articular surfaces, for example interphalangeal joints.
2. Complex joint(art. composite), having more than two articular surfaces, for example the elbow joint. A complex joint consists of several simple joints in which movements can be performed separately. The presence of several articulations in a complex joint determines the commonality of their ligaments.
3. Complex joint(art. complexa), containing intra-articular cartilage, which divides the joint into two chambers (bichamber joint). Division into chambers occurs either completely if the intra-articular cartilage has the shape of a disc (for example, in the temporomandibular joint), or incompletely if the cartilage takes the shape of a semilunar meniscus (for example, in the knee joint).
4. Combined joint is a combination of several isolated joints, located separately from each other, but functioning together. These are, for example, both temporomandibular joints, proximal and distal radioulnar joints, etc. Since a combined joint represents a functional combination of two or more anatomically separate joints, this differs from complex and complex joints, each of which, being anatomically unified, composed of functionally different compounds.

According to form and function, the classification is carried out as follows. The function of a joint is determined by the number of axes around which movements occur. The number of axes around which movements occur in a given joint depends on the shape of its articular surfaces. For example, the cylindrical shape of a joint allows movement only around one axis of rotation. In this case, the direction of this axis will coincide with the axis of location of the cylinder itself: if the cylindrical head is vertical, then the movement occurs around the vertical axis (cylindrical joint); if the cylindrical head lies horizontally, then the movement will occur around one of the horizontal axes coinciding with the axis of the head, for example, the frontal one (trochlear joint).
In contrast, the spherical shape of the head makes it possible to rotate around multiple axes that coincide with the radii of the ball (ball-and-socket joint).
Consequently, there is complete correspondence between the number of axes and the shape of the articular surfaces: the shape of the articular surfaces determines the nature of the movements of the joint and, conversely, the nature of the movements of a given joint determines its shape (P. F. Lesgaft).

Here we see the manifestation of the dialectical principle of the unity of form and function. Based on this principle, we can outline the following unified anatomical and physiological classification of joints.

Uniaxial joints.

1. Cylindrical joint , art. trochoidea. A cylindrical articular surface, the axis of which is located vertically, parallel to the long axis of the articulating bones or the vertical axis of the body, provides movement around one vertical axis - rotation, rotatio; such a joint is also called a rotational joint.

2. Trochlear joint , ginglymus (example - interphalangeal joints of the fingers). Its trochlear articular surface is a transversely lying cylinder, the long axis of which lies transversely, in the frontal plane, perpendicular to the long axis of the articulating bones; therefore, movements in the trochlear joint are performed around this frontal axis (flexion and extension). The guide grooves and ridges present on the articular surfaces eliminate the possibility of lateral slippage and promote movement around a single axis. If the guide groove of the block is not perpendicular to the axis of the latter, but at a certain angle to it, then when it is extended, a helical line is obtained. Such a trochlear joint is considered to be screw-shaped (for example, the shoulder-ulnar joint). The movement in the helical joint is the same as in the pure trochlear joint. According to the patterns of arrangement of the ligamentous apparatus, in a cylindrical joint the guide ligaments will be located perpendicular to the vertical axis of rotation, in a trochlear joint - perpendicular to the frontal axis and on its sides. This arrangement of ligaments holds the bones in their position without interfering with movement.

Biaxial joints.

1. Elliptical joint , articulatio ellipsoidea (example - wrist joint). The articular surfaces represent segments of an ellipse: one of them is convex, oval in shape with unequal curvature in two directions, the other is correspondingly concave. They provide movements around 2 horizontal axes, perpendicular to each other: around the frontal - flexion and extension, and around the sagittal - abduction and adduction. Ligaments in elliptical joints are located perpendicular to the axes of rotation, at their ends.

2. Condylar joint , articulatio condylaris (example - knee joint). The condylar joint has a convex articular head in the form of a protruding rounded process, close in shape to an ellipse, called the condyle, condylus, which is where the name of the joint comes from. The condyle corresponds to a depression on the articular surface of another bone, although the difference in size between them can be significant. The condylar joint can be considered a type of ellipsoidal joint, representing a transitional form from the trochlear joint to the ellipsoidal joint. Therefore, its main axis of rotation will be the frontal one. The condylar joint differs from the trochlear joint in that there is a large difference in size and shape between the articulating surfaces. As a result, in contrast to the trochlear joint, movements around two axes are possible in the condylar joint. It differs from the ellipsoid joint in the number of articular heads. Condylar joints always have two condyles, located more or less sagittally, which are either located in the same capsule (for example, the two femoral condyles involved in the knee joint), or are located in different articular capsules, as in the atlanto-occipital joint. Because the heads in the condylar joint do not have a regular elliptical configuration, the second axis will not necessarily be horizontal, as is the case with a typical ellipsoidal joint; it can also be vertical (knee joint). If the condyles are located in different articular capsules, then such a condylar joint is close in function to the ellipsoidal joint (atlanto-occipital joint). If the condyles are close together and are located in the same capsule, as, for example, in the knee joint, then the articular head as a whole resembles a recumbent cylinder (block), dissected in the middle (the space between the condyles). In this case, the condylar joint will be closer in function to the trochlear joint.

3. Saddle joint , art. sellaris (example - carpometacarpal joint of the first finger). This joint is formed by 2 saddle-shaped articular surfaces, sitting “astride” each other, one of which moves along and across the other. Thanks to this, movements are made in it around two mutually perpendicular axes: frontal (flexion and extension) and sagittal (abduction and adduction). In biaxial joints, a transition of movement from one axis to another is also possible, i.e., circular movement (circumductio).

Multi-axis joints.

1. Globular. Ball and socket joint, art. spheroidea (example - shoulder joint). One of the articular surfaces forms a convex, spherical head, the other - a correspondingly concave articular cavity. Theoretically, movement can occur around many axes corresponding to the radii of the ball, but practically among them three main axes are usually distinguished, perpendicular to each other and intersecting in the center of the head: 1) transverse (frontal), around which bending occurs, flexio, when the moving part forms a the frontal plane is the angle open anteriorly, and extension, extensio, when the angle is open posteriorly; 2) anteroposterior (sagittal), around which abduction, abductio, and adduction, adductio occur; 3) vertical, around which rotation occurs, rotatio, inward, pronatio, and outward, supinatio. When moving from one axis to another, a circular motion, circumductio, is obtained. The ball and socket joint is the loosest of all joints. Since the amount of movement depends on the difference in the areas of the articular surfaces, the articular fossa in such a joint is small compared to the size of the head. Typical ball and socket joints have few auxiliary ligaments, which determines their freedom of movement. A type of spherical joint - cup joint , art. cotylica (cotyle, Greek - bowl). Its articular cavity is deep and covers most of the head. As a result, movement in such a joint is less free than in a typical ball-and-socket joint; We have an example of a cup-shaped joint in the hip joint, where such a device contributes to greater stability of the joint.

2. Flat joints , art. plana (example - artt. intervertebrales), have almost flat articular surfaces. They can be considered as the surfaces of a ball with a very large radius, so movements in them are made around all three axes, but the range of movements due to the slight difference in the areas of the articular surfaces is small.

Ligaments in multiaxial joints are located on all sides of the joint.

Stiff joints- amphiarthrosis. Under this name there is a group of joints with different shapes of articular surfaces, but similar in other characteristics: they have a short, tightly stretched articular capsule and a very strong, non-stretchable auxiliary apparatus, in particular short reinforcing ligaments (for example, the sacroiliac joint).

As a result, the articular surfaces are in close contact with each other, which sharply limits movement. Such inactive joints are called tight joints - amphiarthrosis (BNA). Tight joints soften shocks and shocks between bones.
These joints also include flat joints, art. plana, in which, as noted, the flat articular surfaces are equal in area. In tight joints, movements are sliding and extremely insignificant.

Biomechanics of joints.

In the body of a living person, joints play a triple role: 1) they help maintain body position; 2) participate in the movement of body parts in relation to each other and 3) are organs of locomotion (movement) of the body in space.
Since during the process of evolution the conditions for muscular activity were different, joints of different forms and functions were obtained. In shape, the articular surfaces can be considered as segments of geometric bodies of revolution: a cylinder rotating around one axis; an ellipse rotating around two axes, and a ball rotating around three or more axes.

At the joints, movements occur around three main axes.

The following types of joint movements are distinguished:
1. Movement around the front (horizontal) axis - flexion (flexio), i.e. decreasing the angle between the articulating bones, and extension (extensio), i.e. increasing this angle.
2. Movements around the sagittal (horizontal) axis - adduction (adductio), i.e. approaching the median plane, and abduction (abductio), i.e. moving away from it.
3. Movements around the vertical axis, i.e. rotation (rotatio): inward (pronatio) and outward (supinatio).
4. Roundabout Circulation (circumductio), in which a transition is made from one axis to another, with one end of the bone describing a circle, and the entire bone - the figure of a cone.

It is also possible sliding movements articular surfaces, as well as their removal from each other, as is, for example, observed when stretching the fingers.

The nature of movement in the joints is determined by the shape of the articular surfaces. The volume of movement in the joints depends on the difference in the size of the articulating surfaces. If, for example, the glenoid fossa is an arc of 140° in length, and the head is 210°, then the arc of movement will be equal to 70°. The greater the difference in the areas of the articular surfaces, the greater the arc (volume) of movement, and vice versa. Movements in the joints, in addition to reducing the difference in the areas of the articular surfaces, can be limited in various ways brakes, the role of which is performed by some ligaments, muscles, bone protrusions etc. Since increased physical (strength) load, causing working hypertrophy of bones, ligaments and muscles, leads to the growth of these formations and limitation of mobility, different athletes have different flexibility in the joints depending on the type of sport. For example, the shoulder joint has a greater range of motion in track and field athletes and a smaller range of motion in weightlifters. If the braking devices in the joints are especially strongly developed, then movements in them are sharply limited. Such joints are called tight.

Intra-articular cartilage also influences the amount of movement., increasing the variety of movements. Thus, in the temporomandibular joint, which in terms of the shape of the articular surfaces belongs to biaxial joints, due to the presence of an intra-articular disc, three types of movements are possible.

Patterns of ligament arrangement. The strengthening part of the joint are ligaments, ligamenta, which direct and maintain the work of the joints; hence they are divided into guides and retainers. The number of ligaments in the human body is large, therefore, in order to better study and remember them, you need to know the general laws of their location.
1. Ligaments direct movement articular surfaces around a certain axis of rotation of a given joint and are therefore distributed in each joint depending on the number and position of its axes.
2. The ligaments are located: a) perpendicular to this axis of rotation and b) mainly at its ends.
3. They lie in the plane of a given joint movement . Thus, in the interphalangeal joint with one frontal axis of rotation, the guide ligaments are located on its sides (ligg. collateralia) and vertically. In the biaxial elbow joint ligg. collateralia also run vertically, perpendicular to the frontal axis, at its ends, a lig. anulare is located horizontally, perpendicular to the vertical axis. Finally, in a multiaxial hip joint, the ligaments run in different directions.

SPINAL COLUMN AS A WHOLE

The spinal column is part of the axial skeleton and represents the most important supporting structure of the body, it supports the head and the limbs are attached to it. The movements of the body depend on the spinal column. The spinal column also performs a protective function in relation to the spinal cord, which is located in the spinal canal. These functions are provided by the segmental structure of the spinal column, in which rigid and flexible-elastic elements alternate.

The length of the spinal column in an adult man of average height (170 cm) is approximately 73 cm, with the cervical region accounting for 13 cm, the thoracic region - 30 cm, the lumbar region - 18 cm, and the sacrococcygeal region - 12 cm. The spinal column in women is on average 3-5 cm shorter and amounts to 68-69 cm. The length of the spinal column is about 2/5 of the entire length of the body of an adult. In old age, the length of the spinal column decreases by approximately 5 cm or more due to an increase in the curvature of the spinal column and a decrease in the thickness of the intervertebral discs.

The spinal column is divided into cervical, thoracic, lumbar, sacral and coccygeal parts. The first three consist of separated vertebrae interconnected by a complex system of connections. In the last two parts, complete or incomplete fusion of bone elements occurs, which is due to their predominantly supporting function.

A characteristic feature of the human spinal column is its S-shape, due to the presence of four bends. Two of them are convexly facing forward - these are cervical and lumbar lordosis, and two are facing backward - thoracic and sacral kyphosis.

Curvatures of the spinal column are outlined in the prenatal period. In a newborn, the spine has a slight dorsal curvature with mild lordosis and kyphosis. After birth, the shape of the spinal column changes due to the development of body statics. Cervical lordosis appears when the child begins to hold his head up; its formation is associated with tension in the neck and back muscles. Sitting increases kyphosis of the thoracic spine. Straightening the body, standing and walking cause the formation of lumbar lordosis. After birth, the characteristic curvature of the sacrum, which is already present in the fetus for 5 months, increases. The final modeling of the cervical and thoracic curves occurs by the age of 7, and lumbar lordosis fully develops during puberty. The presence of bends increases the spring properties of the spinal column.

The severity of the curvature of the spinal column varies individually. In women, lumbar lordosis is more pronounced than in men.

A person’s posture depends on the shape of the spinal column. There are three forms of posture:

1) normal,

2) with pronounced curves of the back,

3) with smoothed curves (the so-called “round back”).

Increased thoracic kyphosis leads to stooping. By the age of 50, the curves of the spine begin to smooth out. Some people develop general kyphosis of the spinal column in old age. The reason for these changes in posture is the flattening of the intervertebral discs, weakening of the ligamentous apparatus of the spine, and decreased tone of the back extensor muscles. This is facilitated by a sedentary lifestyle, improper work and rest patterns. Physical exercises allow you to maintain the shape of your spine and good posture for a long time. It is not for nothing that military personnel and athletes in old age maintain correct body posture.

CONNECTION OF VERTEBRES AND MOVEMENT OF THE SPINAL COLUMN

The vertebrae are connected to each other both continuously, through cartilaginous and fibrous connections, and through joints. Intervertebral discs are located between the vertebral bodies. Each disc consists of an annulus fibrosus, located along the periphery, and a nucleus pulposus, which occupies the central part of the disc. There is often a small cavity inside the disc. The fibrous ring is built from plates, the arrangement of fibers in which is similar to the orientation of fibers in osteons. The nucleus pulposus consists of mucous tissue and can change its shape. When the spinal column is loaded, the internal pressure in the core increases, but it cannot compress. The intervertebral disc as a whole plays the role of a shock absorber during movements, thanks to it there is an even distribution of forces between the vertebrae. Up to 80% of the weight of the overlying parts of the body is transmitted through the intervertebral discs.

The greatest height of individual discs in the cervical spine is 5-6 mm, in the thoracic spine – 3-4 mm, in the lumbar spine – 10-12 mm. The thickness of the disc changes in the anteroposterior direction: so between the thoracic vertebrae the disc is thinner in the front, between the cervical and lumbar vertebrae, on the contrary, it is thinner in the back.

The ultimate compressive strength of intervertebral discs is 69-137 kg/cm 2 at an average age, while for vertebral bodies it is only 26 kg/cm 2 . Therefore, under excessive loads, as, for example, when pilots eject, the vertebral bodies are more often damaged than the discs connecting them.

The ligamentous apparatus of the spinal column plays a large role in its stabilization. The straightened position of the body is maintained with little activity of the own back muscles. With maximum flexion of the torso, these muscles relax, and the entire load falls on the ligaments. Therefore, lifting weights in this position is dangerous for the ligaments and joints of the spine.

Movements of the spinal column are carried out by the intervertebral discs and facet joints. The latter are formed by the articular processes of adjacent vertebrae and belong to the flat joints. The shape of the articular surfaces allows combined sliding in different directions. The pair of facet joints, together with the intervertebral disc, form the “movement segment” of the spinal column. Movements in the segments are limited by ligaments, articular and spinous processes and other factors, so the range of movements in one segment is small. However, many segments take part in real movements, and their total mobility is very significant.

In the spinal column, when skeletal muscles act on it, the following movements are possible: flexion and extension, abduction and adduction (lateral flexion), torsion (rotation) and circular movement.

Flexion and extension occurs around the frontal axis. When flexing, the vertebral bodies bend forward, the spinous processes move away from each other. The anterior longitudinal ligament relaxes, and the tension of the posterior longitudinal ligament, ligamentum flavum, interspinous and supraspinous ligaments inhibits this movement. When extending, the spinal column bends back, and all its ligaments relax except the anterior longitudinal ligament, which, when stretched, inhibits the extension of the spinal column.

Abduction and adduction take place around the sagittal. When the spinal column is abducted, the tension of the ligamentum flavum, the capsules of the facet joints, and the intertransverse ligaments located on the opposite side limit this movement.

Rotation The spinal column has a total volume of up to 120º. During rotation, the nucleus pulposus of the intervertebral discs plays the role of the articular head, and the tension of the fibrous rings of the intervertebral discs and the yellow ligaments inhibits this movement.

The direction and amplitude of movements in different parts of the spinal column are not the same. The cervical vertebrae have the greatest mobility. The connections of the atlas and the axial vertebra have a special structure here. The atlanto-occipital and atlanto-axial joints they form together constitute a complex combined multi-axial joint in which head movements occur in all directions. The atlas plays the role of a bone meniscus.

The connections of the atlas and axial vertebra are complemented by a highly differentiated ligamentous apparatus. It is necessary to especially highlight the transverse atlas ligament, which forms a synovial connection with the tooth of the axial vertebra and prevents its displacement back into the lumen of the spinal canal, where the spinal cord is located. Ligament ruptures and dislocations in the atlanto-axial joint are fatal due to possible damage to the spinal cord. Movements between the remaining cervical vertebrae occur around all three axes. The range of motion increases due to the relative thickness of the intervertebral discs. Bending forward is accompanied by sliding of the vertebral bodies, so that the overlying vertebra can bend over the edge of the underlying one.

The mobility of the thoracic vertebrae is limited by the thin intervertebral discs, the rib cage and the location of the articular and spinous processes.

In the lumbar part of the spinal column, thick intervertebral discs allow flexion, extension, and lateral flexion. Rotation here is almost impossible due to the location of the articular processes in the sagittal plane. Movement is most free between the lower lumbar vertebrae. This is the center of most general movements of the torso.

Characteristic of the spinal column is a combination of rotation and lateral flexion. These movements are possible to a greater extent in the upper parts of the spine and are very limited in its lower parts. In the thoracic part, during lateral flexion, the spinous processes turn towards the concavity of the spine, and in the lumbar part, on the contrary, towards the convexity. Maximum lateral flexion occurs at the lumbar spine and its connection with the thoracic spine. Combined rotation is expressed by rotation of the vertebral bodies in the direction of flexion.

The sacrococcygeal joint also has some mobility in young people, especially women. This is of significant importance during childbirth, when, under the pressure of the fetal head, the tailbone deviates back 1-2 cm and the exit from the pelvic cavity increases.

The range of motion of the spinal column decreases significantly with age. Signs of aging appear here earlier and are more pronounced than in other parts of the skeleton. These include degeneration of intervertebral discs and articular cartilage. Intervertebral discs become more fibrous and loosen, lose their elasticity and seem to be squeezed out of the vertebrae. Calcification of the cartilages occurs, and in some cases, ossifications appear in the center of the discs, which leads to the fusion of adjacent vertebrae. Following the discs, the vertebrae change. The vertebral bodies become porous, and osteophytes form along their edges. The height of the vertebral bodies decreases, often they acquire a wedge-shaped shape, which leads to flattening of the lumbar lordosis. The width of the vertebrae in the frontal plane increases along the upper and lower edges; the vertebrae take on a “coil-shaped” appearance. Bone growth occurs along the edges of the articular surfaces of the vertebrae. One of the most common manifestations of aging of the spinal column is ossification of the anterior longitudinal ligament, which is clearly visible on radiographs.

The pelvic bones and sacrum, connected by the sacroiliac joint and the pubic symphysis, form the pelvis. The pelvis is a bony ring, inside of which there is a cavity containing the insides. The pelvic bones with the iliac wings turned to the sides provide reliable support for the spinal column and abdominal viscera. The pelvis is divided into 2 sections: the large pelvis and the small pelvis. The boundary between them is the boundary line.

Big pelvis bounded posteriorly by the body of the fifth lumbar vertebra, on the sides by the wings of the ilium. The large pelvis has no walls in front.

Small pelvis It is a bone canal narrowed downwards. The upper aperture of the small pelvis is limited by the border line, and the lower aperture (exit from the small pelvis) is limited behind by the coccyx, on the sides by the sacrotuberous ligaments, ischial tuberosities, branches of the ischial bones, lower branches of the pubic bones, and in front by the pubic symphysis. The posterior wall of the pelvis is formed by the sacrum and coccyx, the anterior wall is formed by the lower and upper branches of the pubic bones and the pubic symphysis. From the sides, the pelvic cavity is limited by the inner surface of the pelvic bones below the border line, the sacrotuberous and sacrospinous ligaments. On the lateral wall of the pelvis there are the greater and lesser sciatic foramina.

When the human body is in a vertical position, the upper aperture of the pelvis is inclined anteriorly and downward, forming an acute angle with the horizontal plane: in women - 55-60°, in men - 50-55°.

In the structure of the adult pelvis there are clearly expressed sexual characteristics. Women's pelvis is lower and wider than men's. The distance between the spines and crests of the iliac bones is greater in women, since the wings of the iliac bones are more turned to the sides. The promontory in women protrudes less forward than in men, so the upper aperture of the female pelvis has a more rounded shape. The angle of convergence of the lower branches of the pubic bones in women is 90-100°, and in men – 70-75°. The pelvic cavity in men has a clearly defined funnel-shaped shape; in women, the pelvic cavity approaches a cylinder. In men, the pelvis is higher and narrower, while in women it is wider and shorter.

The size and shape of the pelvis are of great importance for the birth process. Knowing the size of the pelvis is necessary to predict the course of labor.

When measuring a large pelvis, 3 sizes are determined:

1. The distance between the two anterior superior iliac spines (distantia spinarum) is 25-27 cm.

2. The distance between the crests of the iliac bones (distantia cristarum) is 28-29 cm.

3. The distance between the greater trochanters of the femurs (distantia trochanterica) is 30-32 cm.

When measuring the pelvis, the following dimensions are determined:

1. External direct size - the distance from the symphysis to the recess between the V lumbar and I sacral vertebrae - 20-21 cm. To determine the true direct size of the entrance to the pelvis, true, or gynecological, conjugates (the distance between the promontory and the most posteriorly protruding point of the pubic symphysis) subtract 9.5-10 cm, get 11 cm.

2. The distance between the anterosuperior and posterosuperior iliac spines (lateral conjugate) is 14.5-15 cm.

3. To determine the transverse size of the entrance to the small pelvis (13.5-15 cm), divide distantia cristarum in half or subtract 14-15 cm from it.

4. The size of the outlet from the small pelvis is the distance between the inner edges of the ischial tuberosities (9.5 cm) plus 1.5 cm for the thickness of the soft tissues - a total of 11 cm.

5. The direct size of the outlet from the pelvis is the distance between the coccyx and the lower edge of the symphysis (12-12.5 cm) and minus 1.5 cm for the thickness of the sacrum and soft tissues - only 9-11 cm.

FOOT AS A WHOLE

The bones of the foot have significantly less mobility than the bones of the hand, as they are adapted to perform a supporting function. Ten bones of the foot: navicular, three wedge-shaped, cuboid, five metatarsal bones - are connected to each other using “tight” joints and serve as the solid base of the foot. According to the concept of G. Pisani, in anatomical and functional terms, the foot is divided into the heel and talus parts. The calcaneal part, which includes the calcaneus, cuboid, IV and V metatarsals, performs a predominantly passive static function. The talus, represented by the talus, navicular, sphenoid, I, II, III metatarsal bones, has an active static function.

The bones of the foot, articulating with each other, form 5 longitudinal and 2 transverse (tarsal and metatarsal) arches.

I - III longitudinal arches of the foot do not touch the plane of support when the foot is loaded, so they are spring, IV, V - adjacent to the support area, they are called supporting The tarsal arch is located in the area of ​​the tarsal bones, the metatarsal arch is in the area of ​​the heads of the metatarsal bones. Moreover, in the metatarsal arch, the planes of support touch only the heads of the first and fifth metatarsal bones. Due to the arched structure of the foot, it does not rest on the entire plantar surface, but has constant 3 points of support: the calcaneal tubercle at the back and the heads of the first and fifth metatarsal bones at the front. All longitudinal arches of the foot begin on the heel bone. And from here the lines of the arches are directed forward along the metatarsal bones. The longest and highest is the 2nd longitudinal arch, and the lowest and shortest is the 5th. At the level of the highest points of the longitudinal arches, a transverse arch is formed.

The arches of the foot are held in place by the shape of the bones that form them, ligaments (passive tightening of the arches of the top) and muscles (active tightening). To strengthen the longitudinal arches, the long plantar ligament, plantar calcaneonavicular ligament, and plantar aponeurosis are of great importance as passive tightening. The transverse arch of the foot is supported by transverse ligaments of the sole (deep transverse metatarsal ligament, interosseous metatarsal ligaments). The muscles also help support the arches of the feet. The longitudinally located muscles and their tendons, attached to the phalanges of the fingers, shorten the foot and thereby help to “tighten” its longitudinal arches, and the transversely located muscles, narrowing the foot, strengthen its transverse arch. When active and passive puffs are relaxed, the arches of the feet drop, the foot flattens, and flat feet develop.

Thanks to the arched structure of the foot, the weight of the body is evenly distributed over the entire foot, shaking the body when walking, running, jumping is reduced, since the arches play the role of shock absorbers. Arches also help the foot adapt to walking and running on uneven terrain.

Test questions for the lecture:

1. Development of bone joints in phylogenesis.

2. Classification of bone connections.

3. Functional anatomy of syndesmoses.

4. Functional anatomy of synchrodrosis, synostosis, semi-joints.

5. Classification of joints according to the number of articular surfaces and the shape of the articular surfaces.

6. Classification of joints according to the number of axes of motion.

7. General characteristics of combined joints and complex joints.

8. The structure of the main and auxiliary elements of joints.

9. Basic principles of joint biomechanics.

10Functional and morphological features of the spinal column as a whole.

Joints arose in the body after hard tissues (bone, cartilage) formed into a support organ and began to perform this function both in the body itself and in environmental conditions (on land, in water, in the air). However, not all bones or cartilage are connected to each other using joints. In some cases, in the absence of diastasis, two bones are connected to each other by dense connective tissue, similar to an interosseous membrane. In other cases, a continuous cartilaginous connection is formed between adjacent bones. Sometimes initially independent bones grow together into a single bone mass. Consequently, some special conditions are necessary for the formation of joints.

To determine what these conditions are, let's first analyze the simpler forms of bone connection. Thus, in conditions when a bone is constantly displaced relative to another bone, connective tissue adhesions are formed - in the form of a membrane connection or various kinds of sutures. These types of connections allow the bones to move relative to each other and at the same time hold them quite firmly at a certain distance. In cases where the range of bone displacement (for example, with age) gradually decreases, the ligamentous apparatus becomes denser and shorter. And finally, a moment comes when two different bones grow together. The boundaries between them cannot be determined.

In the first case, i.e. with a ligamentous connection, the bones move relative to each other over a wide range, and also move away from each other at the moment of displacement. In the second case, not only does the range of displacement decrease, but also the bones move closer together, which inevitably leads to increased pressure from one bone on another.

A completely different picture is observed in the case of significant bone displacements and the presence of pressure from one bone on another. It is under these conditions that joints with all their characteristic elements are formed. That this is exactly the case is evidenced by different types of joints and those components that are essential attributes of each joint.

To successfully control the function, it is necessary to know, at least in general terms, the biomechanics and structural features of joints (A general analysis of large joints is given as the most obvious example).

Shoulder joint (articulatio humeri). Formed by the head of the humerus and the glenoid cavity of the scapula. It has a spherical shape and is the most mobile joint in humans; surrounded by a thin and freely sagging bag. The ligamentous apparatus is represented only by the coracobrachial ligament.

Three mutually perpendicular main axes of rotation can be distinguished. Around the transverse axis, flexion (forward movement) and extension are carried out; around the anterior-posterior axis - abduction and adduction; around the vertical axis - pronation (inward rotation) and supination (outward rotation); in addition, cone-shaped rotation (circumduction) is possible.

Movements localized strictly in the shoulder joint are performed only within a relatively small range. In all other cases, they are joined by friendly movements of the entire girdle of the upper limbs (scapula, collarbone) and the spinal column.

The muscles play the main role in maintaining the contact of articulating bones, but they often fail to cope with it. With significant fatigue and reflex relaxation of the muscles, the head can separate from the fossa, and after the load stops, return to its place. This phenomenon is encountered by those who regularly carry quite heavy loads. The coincidence of the articular surfaces is also disrupted when performing movements of extreme range - especially flexion and abduction. This, in particular, explains the increased likelihood of injury to the shoulder joint, which can only be reduced with regular strength training of the muscles surrounding it.

Maximum flexion and abduction in the shoulder joint is limited by the thrust of the humerus into the humeral process of the scapula (acromion). Some further movement in this direction is possible even after the bones come into contact - due to disruption of the contact of the head and the fossa. In some cases, the sagging joint capsule may end up between the bone abutments; its infringement occurs, which is not eliminated immediately. Passive extension is inhibited by strong stretching of the muscles, ligaments of the joint and, to a much lesser extent, by the tension of its bursa.

The amplitude of extension and abduction (especially during active execution) depends on the rotation of the arm inward or outward. Supination increases extension by 15-20°. When the arm pronates, its abduction increases by 20-40°.

Elbow joint (articulatio cubiti). It is a combination of the humeroulnar and radioulnar proximal joints, which have a common bursa and articular cavity.

The main load when performing most movements is borne by the shoulder-elbow joint. It belongs to the trochlear type and has only one - transverse - axis of rotation around which flexion and extension occur. The humeral joint has a spherical shape, the proximal radioulnar joint has a cylindrical shape. Thanks to these joints and the distal radioulnar joint, pronation and supination of the forearm are carried out around the longitudinal axis of the joint. This axis passes through the center of the capitate eminence of the humerus and the center of the head of the ulna. There is also an anterior-posterior axis of rotation, perpendicular to the first two. However, minor movements around this axis are possible only if the forearm is bent relative to the shoulder at an angle of 90°.

The arc of the trochlear humerus reaches 320°, and the trochlear notch of the ulna reaches 180°. This ratio allows for movement with a range of about 140°.

The ulnar and coronoid processes of the ulna, resting against the bottom of the corresponding fossae of the humerus, serve as limiters of flexion and extension.

The lateral (collateral) ligaments - ulnar and radial - strengthen the joint during passive abduction and adduction of the forearm, as well as with significant pronation and supination. The annular ligament of the radius plays an auxiliary role in these movements.

In the vast majority of people, flexion and extension are performed in full and do not require additional training to increase mobility. Natural pronation-supination in everyday life is also quite enough. Special needs may arise when practicing certain sports: basketball, table tennis, artistic and rhythmic gymnastics, etc. Special exercises (passive rotations of the forearm straightened and bent at an angle of 90°) can increase the amplitude of pronation-supination from 130-140° to 160-180° (in all cases, the magnitude of these movements is measured by the amplitude of rotation of the hand).

With the forearm bent, slight abduction and adduction can be performed passively, under the influence of an external force. This occurs, for example, in all throwing movements of a “whip-like”, ballistic nature. It should be emphasized that these movements are “not provided for” by the structure of the elbow joints. During their execution, the radial and ulnar collateral ligaments are overstrained and, if the load is high enough, injured.

Thus, when training the elbow joint, the only goal is usually to strengthen it. There is no need to develop mobility - it is enough to maintain it at the level necessary to perform the assigned motor tasks. On the contrary, there may be a need to limit excessive mobility - for example, congenital hyperextension in the elbow joint. This fairly common phenomenon - mainly of hereditary origin - is aggravated by weakness of the muscles of the shoulder and forearm. In some cases, hyperextension reaches 30° (in this case it is always accompanied by a noticeable abduction of the forearm). It creates the impression of unnaturalness, fragility, and vulnerability.

Excessive mobility can be eliminated by powerful forceful exertion of the arms (push-ups, pull-ups, lifting weights) with a limited (to the position of the extension of the shoulder) range of motion of the forearm. Skiing and rowing also have a beneficial effect.

Wrist joint (articulatio radiocarpea). Formed by the articular surface of the radius and the ellipsoidal surface of the bones of the proximal row of the wrist (scaphoid, lunate and triquetrum). The ulna, equipped at the lower end with a cartilaginous fibrous disc, also takes part in the formation of the joint, contributing (especially when resting on the hand) to distribute pressure over a large area.

The wrist joint performs flexion, extension, adduction and abduction of the hand. Its pronation and supination occur together with the rotation of the distal ends of the forearm bones. Slight true rotation of the hand is possible only under the influence of external force, due to the elasticity of the cartilage and some mutual removal of the articular surfaces. The amplitude of flexion and extension increases due to the mobilization of small mobility in the midcarpal and intercarpal joints, forming a complex kinematic chain.

The ligamentous apparatus of the wrist joint is very complex. Going in a variety of directions, the ligaments densely entwine it on all sides. They are also located between the bones. The main ones are the ulnar and radial lateral (collateral) ligaments of the wrist.

Abduction and adduction of the hand are limited by the contact of the corresponding carpal bones and the styloid processes present at the ends of the ulna and radius. Impact of these motion restrictors is one of the most common causes of injury to the wrist joint. The two main ligaments of the joint are attached to these processes - the lateral ulnar and lateral radial.

Hip joint (articulatio coxae). Formed by the acetabulum of the pelvic bone and the head of the femur. It has a strong thick capsule, reinforced by the iliofemoral, ischiofemoral and pubofemoral ligaments. These ligaments are highly stressed during extension and rotation of the leg from the main stance position and remain passive during flexion. The ligament of the femoral head, located inside the joint capsule, is stretched only with extreme adduction of the hip. In all other cases, it, like a pillow, absorbs impacts of the articular surfaces.

The hip joint has a spherical shape with three main axes of rotation, around which flexion and extension, abduction and adduction, pronation and supination occur. It has less mobility than the shoulder joint. This is explained by greater congruence (coincidence) of the articular surfaces, a more powerful ligamentous apparatus and the surrounding massive muscles. It is almost impossible to fix isolated movements of the thigh in the hip joint without special devices, since they are always accompanied by concomitant movements of the pelvis and spine. (This explains the significant discrepancies in the data of various authors on the maximum range of hip movements.)

Constant tension in muscles and ligaments is already observed in a normal standing position. As a result, the hip is gradually fixed in a certain familiar average position, and its mobility is limited. Thus, special gymnastics for the joint, aimed primarily at preserving the natural range of motion and appropriate training of all its elements, becomes necessary.

Rational training over several months can increase the amplitude of maximum hip flexion by 30-40° or more.

Extension at the hip joint is inhibited by the tension of the powerful iliofemoral ligament. Actually, it is already tense in the position of the main post and further extension can be extremely insignificant.

Hip abduction limits the contact of the bones - the greater trochanter with the upper edge of the acetabulum. Therefore, any abduction (especially a sharp or swinging one) must be performed carefully. Increasing hip mobility in this direction requires many years of systematic training. It should be remembered that a supinated (externally rotated) hip can be abducted much further than a non-supinated one, since in this case the greater trochanter leaves the plane of movement and no longer limits it.

The amount of pronation and especially supination quickly decreases with age. Systematic exercises make it possible not only to maintain, but also to significantly increase the amplitude of these movements, affecting mainly the muscles surrounding the joint and the cartilaginous edges of the articular fossa.

Knee joint (articulatio genus). Combines the properties of the trochlear and spherical joints. From the extended position, only flexion is possible. As you flex, due to a decrease in the radius of curvature of the femoral condyles, the fibular and tibial collateral ligaments relax. The joint receives another degree of freedom; Limited pronation and supination of the lower leg become possible. The axis of these movements runs vertically - approximately in the center of the medial femoral condyle.

The maximum amplitude of these movements is achieved when the tibia is flexed 90°. These movements are performed by relatively weak muscles, which are also in unfavorable biomechanical conditions, which increases the risk of injury to the joint when pronation and supination are performed due to significant external force. (Such injuries are typical, for example, for skiers who have to control rather long skis by intensely twisting the knee joint in one direction or the other.)

The congruence of the articular surfaces is increased by fibrocartilaginous concave spacers - menisci. They also help soften shocks and shocks and distribute the pressure of the condyles over a large supporting surface.

Located in the joint cavity between the condyles of the femur, the anterior and posterior cruciate ligaments strengthen the joint - especially during large-scale movements and movements associated with rotation.

The patella is a sesamoid bone. It increases the leverage of the quadriceps muscle.

The vast majority of people experience complete flexion of the tibia, up to the point of contact with the back of the thigh. Optimal extension - to a position where the lower leg is a continuation of the femur and forms one straight line with it - is carried out without hindrance. This eliminates the need for any training for these movements - other than training to strengthen the joint.

The hyperextension that occurs is blocked by increasing the strength of the lateral ligaments and the bursa (especially in its posterior part), as well as the elasticity of the muscles of the lower leg and thigh, which spread over the joint. Using a specially simulated load, it is possible to increase the strength of the attachment of the menisci to the articular surface of the tibia, which can be damaged under strong impact loads directed from top to bottom and torn from their attachment points as a result of hyperextension and excessive rotation.

It is also necessary and possible to strengthen the cruciate ligaments, which prevent the femur from sliding forward and backward and are greatly strained when the tibia rotates. Strengthening is carried out using moderate, controlled and regular loads.

With strong bending under load, a “dead position” occurs, as weightlifters say, when the powerful forces of the thigh muscles are only to a small extent involved in extending the leg. Most of them are spent on deformation of the knee joint: its cup is pressed between the condyles of the femur; all elements of the joint are overstrained - cartilage, ligaments, menisci, numerous synovial bursae. The attachment of the quadriceps tendon on the tibia is also overloaded.

The specific structure of the knee joint causes the formation of X-shaped and O-shaped deviations, which depend on the different relative sizes of the external and internal condyles of the femur. When creating a training regimen, this circumstance must be taken into account. Significant deviations from the norm can become an obstacle to successful participation in some sports. Strengthened training in combination with orthopedic measures can have only a partial normalizing effect.

If, with O-shaped deviations, we measure the length of the leg from the trochanteric point to the support and the distance between the internal epicondyles of the femurs, and then multiply this distance by 100 and divide by the length of the limb, then we get the O-shaped index. With an X-shape, the distance between the inner ankles, multiplied by 100, is divided by the length of the leg. The corresponding knee joint index is calculated. Deviations with an index of up to 3.0 should be considered insignificant; from 3.5 to 5.0 - noticeable; over 5.0 - large.

Ankle joint (articulatio talocruralis). Formed by the bones of the tibia and the talus. It has a block-like shape and one, transverse, axis of rotation. Because the trochlea of ​​the talus is somewhat narrower posteriorly than anteriorly, as the joint flexes, it exhibits limited ability for passive lateral and rotational movements. However, these movements are quite difficult to isolate, since they are masked by the mobility of the distal tarsal joints (subtalar, talocalcaneal-navicular, etc.), with which the ankle joint forms a kinematic chain.

The ligaments of the ankle joint are concentrated on the outer and inner sides. They selectively tense at the limit of flexion and extension. At the same time, when the foot is abducted, all the ligaments located on the inside of the joint are sharply and strongly stretched; at the moment of adduction - all ligaments of the outer fan. Movements in intermediate planes increase the unevenness and asynchrony of ligament tension, which is one of the reasons for increased joint trauma.

Extreme flexion and extension of the foot at the ankle joint limits the emphasis of the edges of the tibia on the neck or on the posterior process of the talus. Long-term exercise can slightly change the configuration of these movement limiters and significantly increase the mobility of the foot. Aging of an underused ankle joint begins precisely at the anterior and posterior edges of the talus trochlea.

Spine and body flexibility. The flexibility of the spine (and, to a large extent, of the entire body) is determined by the connections of the vertebral bodies. The angular displacement of the bodies occurs due to the elastic deformation of the intervertebral discs. The amount of angular displacement of two adjacent vertebrae during tilting and bending depends mainly on the height and elasticity of the discs. The thickest discs are located in the lumbar spine, the thinnest are in the middle part of the thoracic spine, where the relative mobility of adjacent vertebrae is extremely low. In the cervical region, the discs are quite thin, but the height of the vertebral bodies is much smaller. Therefore, the flexibility of the cervical spine is approximately the same as that of the lumbar spine.

Movements of the spinal column are carried out around three mutually perpendicular axes: transverse - flexion and extension; anterior-posterior - tilts to the right and left; vertical - turns right and left. A complex combination of these movements is carried out with a circular rotation of the torso.

Individual fluctuations in the flexibility of various parts of the spine are very large. It has been noted that in people with little flexibility, the degree of angular displacement of the vertebral bodies is regulated primarily by ligaments running along the spine. With good flexibility, the muscles of the torso come to the fore, which are naturally more extensible. The less flexibility of the thoracic region when performing any movements is explained primarily by the fact that ribs are attached to its vertebrae, limiting the possibility of angular displacement of the vertebrae.

The cervical spine retains some autonomy during body movements and does not necessarily participate in these movements. It also implements flexion-extension, tilting left and right, and rotation. This department requires special exercises and regular joint work.

Chest joints. Located at the junction of the ribs with the sternum and spine. These are flat, inactive joints that allow only slight displacement of the bones. Some of them (sternocostal) are even predisposed to overgrowing with cartilage. This tendency increases with age and especially with a passive lifestyle.

No matter how small the mobility of these joints is, its significance is very great: thanks to it, with great effect and with less energy expenditure, the volume of the chest changes during inhalation and exhalation. There is evidence that a large vital capacity of the lungs is always combined with greater mobility of the ribs, which can be trained. In addition to special exercises, rowing, swimming, and skiing have a beneficial effect on the mobility of the ribs. It should be noted that spinal flexibility training is also an effective means of increasing rib mobility.

Shoulder girdle joints. Connect the sternum to the collarbone and the collarbone to the scapula. They have both their own mobility and dependent mobility, which is mobilized during all kinds of hand movements and increases their maximum amplitude. This is especially important when the intrinsic mobility of the shoulder joint is already mobilized, but is insufficient.

Since the shoulder girdle takes part in inhalation movements, the high mobility of its joints affects the amount of maximum inhalation and exhalation.

Many classifications of joints can be given, in each case taking as a basis a certain property of them. We will consider only those classifications that will help in solving the problem posed in this book.

All joints can be divided into three groups according to the volume of movements performed.

The first group includes joints with a wide range of motion (shoulder, knee, etc.). These and similar joints are characterized by a large range of movements: their articular surfaces are little congruent, and the difference in the areas of the articular surfaces is very significant; the joint capsule and ligamentous apparatus slightly impede movement. We can say that in this group all the features of the joint, as a type of bone connection, are most clearly expressed.

The second group includes joints with a sharply limited range of motion and semi-joints (flat joints: articulations of the vertebral bodies - articulatio intervertebralis, sacroiliac joint - articulatio sacroiliaca; tight joints. intercarpal joints - articulatio mediocarpea, articulations between the tarsal bones - articulationes intertarsea, etc.; semi-joints, pubic fusion - symphysis pubica; connection ribs with sternum, etc.). The listed types of joints are characterized not only by small volumes of movement, but also by a number of structural features. Thus, the articular surfaces of most joints are almost completely congruent; the difference between the areas of the articular surfaces is absent or insignificant; the ligamentous apparatus is usually well developed and significantly inhibits movement; in some cases (for example, in semi-joints) there is no capsule.

The third group includes joints with a moderate range of motion , occupying an intermediate place between the two previously indicated groups (ankle - articulatio talocruralis, wrist - articulatio radiocarpea, etc.). In these joints, all their components are moderately developed.

The classification of joints by range of motion attracts attention because it emphasizes the role of function in the formation of a joint. If part of the embryo’s limb is isolated from the body (for example, in the area of ​​the future knee joint) and placed in conditions close to the living conditions of the developing organism, then the knee joint will form in the same way as it would develop in the whole embryo: an articular cavity is formed, articular joints are formed ends of bones, capsule, etc. The absence of movements in the joint (and it is known that fetal movement begins in the first months of intrauterine life) leads to the fact that the initially formed joint cavity becomes overgrown, and the articular ends of the bones grow together.

If an adult does not use a limb for a long time and there is no movement in the joint, then after some time the volume of these movements is sharply reduced; subsequently, so-called ankylosis occurs - a complete lack of movement in this joint. Conversely, with systematic exercises to develop mobility in the joint, you can achieve a significant increase in the range of motion.

Two important circumstances follow from these provisions.

• 1. Hereditary predetermination of the formation of joints exists as a potential possibility of specific motor manifestations, the implementation of which occurs in the process of function. Without normal functioning, this opportunity may remain unrealized.
• 2. The volume and number of movements performed significantly affect the structure of the joint and the severity of its components (this will be shown in subsequent sections).

Consequently, the nature and volume of movement in the joint will characterize it as a whole, as well as its individual elements. On the other hand, by the state of the joint elements one can judge the influence of the functional load on a particular joint, i.e. have objective criteria for the development and formation of a particular joint in a given direction. All this allows you to effectively control the morphogenesis and function of the joint.

The human skeleton consists of more than 200 bones, most of which are movably connected by joints and ligaments. It is thanks to them that a person can move freely and perform various manipulations. In general, all joints are structured the same. They differ only in shape, nature of movement and the number of articulating bones.

Joints simple and complex

Classification of joints by anatomical structure

According to their anatomical structure, joints are divided into:

1. Simple. The joint consists of two bones. An example is the shoulder or interphalangeal joints.
2. Complex. A joint is formed by 3 or more bones. An example is the elbow joint.
3. Combined. Physiologically, the two joints exist separately, but function only in pairs. This is how the temporomandibular joints are designed (it is impossible to lower only the left or right side of the jaw, both joints work simultaneously). Another example is the symmetrically located facet joints of the spinal column. The structure of the human spine is such that movement in one of them entails displacement of the other. To understand more precisely the principle of operation, read the article with beautiful illustrations about.
4. Complex. The joint space is divided into two cavities by cartilage or meniscus. An example is the knee joint.

Classification of joints by shape

The shape of the joint can be:

1. Cylindrical. One of the articular surfaces looks like a cylinder. The other has a recess of suitable size. The radioulnar joint is a cylindrical joint.
2. Block-shaped. The head of the joint is the same cylinder, on the lower side of which a ridge is placed perpendicular to the axis. On the other bone there is a depression - a groove. The comb fits the groove like a key to a lock. This is how the ankle joints are designed.
   A special case of trochlear joints is the helical joint. Its distinctive feature is the spiral arrangement of the groove. An example is the shoulder-elbow joint.
3. Ellipsoidal. One articular surface has an ovoid convexity, the second has an oval notch. These are the metacarpophalangeal joints. When the metacarpal sockets rotate relative to the phalangeal bones, complete bodies of rotation are formed - ellipses.
4. Condylekov. Its structure is similar to the ellipsoidal one, but its articular head is located on a bony protrusion - the condyle. An example is the knee joint.
5. Saddle-shaped. In its form, the joint is similar to two nested saddles, the axes of which intersect at right angles. The saddle joint includes the carpometacarpal joint of the thumb, which among all mammals is present only in humans.
6. Spherical. The joint articulates the ball-shaped head of one bone and the cup-shaped notch of the other. A representative of this type of joint is the hip. When the socket of the pelvic bone rotates relative to the femoral head, a ball is formed.
7. Flat. The articular surfaces of the joint are flattened, the range of motion is insignificant. The flat one includes the lateral atlantoaxial joint, connecting the 1st and 2nd cervical vertebrae, or lumbosacral joints.
   A change in the shape of the joint leads to dysfunction of the musculoskeletal system and the development of pathologies. For example, against the background of osteochondrosis, the articular surfaces of the vertebrae shift relative to each other. This condition is called spondyloarthrosis. Over time, the deformity becomes fixed and develops into a permanent curvature of the spine. Instrumental examination methods (computed tomography, radiography, MRI of the spine) help to detect the disease.

Division by nature of movement

The movement of bones in a joint can occur around three axes - sagittal, vertical and transverse. They are all mutually perpendicular. The sagittal axis is located in the front-to-back direction, the vertical axis is from top to bottom, the transverse axis is parallel to the arms extended to the sides.
Based on the number of axes of rotation, joints are divided into:

• uniaxial (these include block-shaped),
• biaxial (ellipsoidal, condylar and saddle-shaped),
• multi-axial (spherical and flat).

Summary table of joint movements

Number of axes Joint shape Examples

One Cylindrical Median Antlantoaxial (located between the 1st and 2nd cervical vertebrae)

One trochlear ulna

Two Ellipsoid Atlanto-occipital (connects the base of the skull with the upper cervical vertebra)

Two Condylar Knee

Two Saddle Carpometacarpal Thumb

Three Ball Shoulder

Three Flat Facet Joints (included in all parts of the spine)

Classification of types of movements in joints:

Movement around the frontal (horizontal) axis - flexion (flexio), i.e. decreasing the angle between the articulating bones, and extension (extensio), i.e. increasing this angle.
Movements around the sagittal (horizontal) axis - adduction (adductio), i.e. approaching the median plane, and abduction (abductio), i.e. moving away from it.
Movements around the vertical axis, i.e. rotation (rotatio): inward (pronatio) and outward (supinatio).
Circular movement (circumductio), in which a transition is made from one axis to another, with one end of the bone describing a circle, and the entire bone - the figure of a cone.

The musculoskeletal system (MSA) is a very complex system responsible for the ability to move the human body in space. Structurally, it is divided into two parts - active (muscles, ligaments, tendons) and passive (bones and joints).

Interesting! The human skeleton is a kind of frame, a support for all other systems of the body. In an adult, it consists of 200 bones, the joints of which can be either fixed or movable.

The movable connection of bones is provided by joints, of which there are 360. For the most part, they are located in the spine, where their number reaches 147 pieces; they provide articulation of the vertebrae with each other and with the ribs.

The main purpose of the articular joint, in addition to ensuring bone mobility, is shock absorption, mitigating the shocks and overloads that our skeleton experiences.

All joints of our body are divided into the following main types:

Provide the most flexible connection between individual bones. They are the most complex structures and consist of several main parts. Synovial include the articular surfaces of the knees, shoulders, elbows, fingers, etc. Their anatomy, depending on the type, is as follows:

Fibrous

In this case, individual bones are attached to each other using cartilage tissue. As a result, the connection is, although inactive, more durable.

In Latin, “fiber” means fiber, which is where this type of compound gets its name. The sternum, ribs, intervertebral discs, as well as the pelvic bones and some skull bones are articulated in a fibrous manner.

Fibrous

In this case, the bones are connected to each other so rigidly that they practically form a monolithic surface. In this case, the connective cartilage tissue hardens so much that it loses all elasticity. The large bones of the cranial vault (frontal, parietal, temporal) articulate in a similar way.

Classification of human joints

Synovial joints of the human skeleton are divided into several types. Due to the large number of different articular joints, a “joint table” has been developed in biology to differentiate them. In modern human anatomy, joints are classified according to several criteria:

1. By the number of surfaces.
2. According to the shape of the surfaces.
3. According to degrees of freedom during movement.

Number of surfaces

The connection of bones can have several articular articulation surfaces, depending on which they are divided into the following types.

Simple joint (simplex)

Simple joints have only two movable articular surfaces, between which there are no additional inclusions. Examples of such joints are the phalanges of the fingers, shoulder or hip joints. Thus, a simple connection is formed by the glenoid cavity of the scapula and the head of the humerus.

Complex (composite)

Such a connection has more than two articular surfaces. This type includes the elbow joint, which is more complex in structure compared to the shoulder joint. They may also have additional inclusions - cartilage or bone. Such structures are called complex and combined joints. Their structure differs from simple ones in that their design may include any additional components:

1. Complex - contain in their structure an intra-articular cartilaginous element (meniscus, or cartilaginous disc). It divides the joint from the inside into two isolated parts. An example of a complex joint is the knee joint, in which the meniscus divides the intra-articular cavity into two halves.

1. Combined - are a combination of several joints isolated from each other, which, despite this, work as a single mechanism. An example is the temporomandibular joint, which is responsible for the mobility of the lower jaw. At the same time, thanks to the complex connection mechanism, its mobility is ensured in several directions at once: up-down, forward-backward, right-left.

The nature of movement (degrees of freedom) of human joints

The joints of individual bones can provide them with different mobility relative to each other. According to the degree of mobility they are divided into:

Uniaxial

They ensure the movement of the connected bones in only one axis (only back and forth or up and down).

Biaxial

Movement in them occurs in two perpendicular planes (for example, vertical and horizontal, or longitudinal and transverse).

Multi-axis

Such a connection of bones, due to their design features, gives them the ability to move along several axes. Multi-axis joints can be three-axis or four-axis.

Bezosnye

They have flat articular surfaces, which allows adjacent bones to perform very limited sliding or rotational movements. Typically, they provide articulation for short bones or bones that require a particularly strong connection.

Shape of the articular surface

Depending on their shape, all joints are divided into several groups. Each of them has its own characteristics - in particular, their shape determines the nature of the movement of the connected bones. Therefore, all groups of joints are associated with the degree of their mobility.

Uniaxial joints are divided according to the shape of the articular surfaces into the following types:

The articular surfaces in this case are located longitudinally, with one of them looking like an axis, and the other looking like a cylinder with a longitudinally cut base. A classic example of a cylindrical articular joint is the median atlantoaxial joint, located in the cervical vertebrae.

Block-shaped

Block-shaped joints resemble cylindrical ones in shape, but the articular surfaces in them are located not longitudinally, but transversely. To limit sideways displacement of the bones, they may have special ridges and indentations that prevent freedom of movement. These include the joints of the phalanges of human fingers or the elbow joints of ungulates.

Helical

At its core, it is a type of block joint. The pattern of the helical structure suggests the presence of peculiar grooves on the surfaces of the epiphysis of one bone, which fit into the corresponding grooves on the epiphysis of the second bone. Thanks to this, the possibility of movement in a spiral is ensured, which is where the second name for joints of this type comes from – spiral-shaped.

Biaxial connections are provided by the following forms of joint structures.

Elliptical

The connecting surface of one of the bones has the shape of a convex ellipse, and the other - a concave ellipse. In the human skeleton, the ellipsoid joints include the atlanto-occipital joint and the joint connecting the femur and tibia.

Condylar

The surface of one bone has the shape of a sphere, and the other has a concave surface in which this sphere is located. The condylar articulation provides mobility of bones in two planes: flexion-extension and rotation to the right and left. In this way, the condylar joint is similar to a spherical one. But, unlike it, it does not allow active rotational movements around a vertical axis. An example is the metacarpophalangeal and knee joint.

Saddle

Both saddle-shaped bones have saddle-shaped depressions at their ends, and these depressions are located perpendicular to each other. This arrangement gives slightly more possibilities when moving. For example, the metacarpal joint of the thumb of humans and primates has a similar design, which allows it to be “opposed” to the rest of the fingers of the hands.

The possibility of such a opposition, from the point of view of biologists, became one of the main reasons for the transformation of monkeys into humans. The presence of the saddle joint allowed our ancestors to use their hands as an active grasping mechanism for holding various tools.

Multiaxial articulation is carried out using joints of the following shape:

Globular

In this case, one of the bones has a ball-shaped head at its end, and the opposite bone has a cavity. As a result, movement is possible in any direction, making ball and socket joints the freest in the human body.

Another name for them is nut-shaped, due to the similarity of the shape of the spherical head with a walnut. A classic example of a ball and socket joint is the shoulder joint between the shoulder blade and the humerus.

Cup-shaped

It is one of the special forms of a spherical joint. The largest human joint, the hip, is articulated in a similar way. In this case, the spherical head is placed in a special “bowl” - the acetabulum. This connection allows a person to move the hip in four directions:

• along the frontal axis – flexion-extension (when squatting, lifting the leg to the stomach);
• along the sagittal axis – abducting the leg to the side and returning it to its original position;
• along the vertical axis – some displacement of the thigh relative to the pelvis when the leg is extended;
• hip rotation;

Flat

In this case, the surfaces of both bones facing each other have a flat or close to it shape. A more precise definition is not “plane”, but “the surface of a sphere of large cross-section.” Such joints enable bones to move in all three axes; however, due to the peculiarities of their design, all these movements are extremely limited in amplitude. For the most part, they play an auxiliary, buffer role. An example of such a structure is the intervertebral joints, joints of the foot and hand.

Amphiarthrosis

They are also “tight joints”. A special type of connection, possible for any surface shape. Its distinctive feature is the presence of a short and tightly stretched capsule, which is surrounded on all sides by strong, practically non-stretchable ligaments.

The articular surfaces of both intersecting bones are pressed very tightly against each other. This design feature significantly limits their ability to move relative to each other. Amphiarthrosis, for example, is the sacroiliac joint. The purpose of such rigid structures is to absorb shocks and impacts experienced by the bones.

Conclusion

So, we looked at what a human joint is, how many there are in our body, what types and characteristics of each joint there are, and where they are located.

Perfect glide for mindless movements

When you see another “snake woman” in “Minute of Fame”, twisting her body almost into pigtails, you understand that the structure of joints and bones that is standard for other people is not about her. What kind of dense fabrics can we talk about - they simply aren’t here!

However, even she has hard tissues - many joints, bones, as well as structures for their connections, according to the classification, divided into several categories.

Classification of bones

There are several types of bones depending on their shape.

Tubular bones have a medullary cavity inside and are formed from compact and spongy substances, performing supporting, protective and motor roles. Divided into:

• long (bones of the shoulders, forearms, thighs, legs), having a biepiphyseal ossification;
• short (bones of both wrists, metatarsals, digital phalanges) with a monoepiphyseal type of ossification.

Bones have a spongy structure, with a predominance of spongy substance in the mass with a small thickness of the covering layer of compact substance. Also divided into:

• long (including costal and sternum);
• short (vertebral bones, carpals, tarsals).

This category also includes sesamoid bone formations, located near the joints, participating in their strengthening and facilitating their activity, but not having a close connection with the skeleton.

Flat shaped bones including categories:

• flat cranial (frontal and parietal), acting as protection and formed from two outer plates of a compact substance with a layer of spongy substance located between them, having connective tissue origin;
• flat bones of both girdles of the limbs (scapular and pelvic) with a predominance of spongy substance in the structure, acting as support and protection, with origin from cartilaginous tissue.

Bones of mixed (endesmal and endochondral) origin with different structures and tasks:

• forming the base of the skull;
• clavicular

Only the bones do not live on their own - they are connected to each other by joints in the most ingenious ways: two, three, at different angles, with varying degrees of sliding against each other. Thanks to this, our body is provided with incredible freedom of static and dynamic poses.

Synarthrosis VS diarthrosis

But not all bone joints should be considered diarthrosis.

According to the classification of bone joints, the following types of joints do not include these:

• continuous (also called adhesions, or synarthrosis);
• semi-mobile.

The first gradation is:

• synostosis - fusion of the boundaries of bones with each other until complete immobility, zigzag “zippers” of sutures in the cranial vault;
• synchondrosis - fusion through a cartilaginous layer, for example, an intervertebral disc;
• syndesmoses - strong “stitching” of a connective tissue structure, the interosseous sacroiliac ligament, for example;
• synsarcoses - when connecting bones using a muscle layer.

The tendon membranes stretched between the paired formations of the forearms and shins, holding them dead next to each other, are also not joints.

As well as semi-movable joints (hemiarthrosis) in the form of the pubic symphysis with a small (incomplete) cavity-gap in the thickness of the fibrocartilaginous suture, or in the form of sacroiliac amphiarthrosis with real articular surfaces, but with an extremely limited range of movements in the semi-joints.

Structure and functions

A joint (discontinuous or synovial joint) can only be considered a movable joint of bones that has all the necessary attributes.

In order for all dysarthrosis to move, there are special formations and auxiliary elements in them in strictly defined places.

If on one bone it is a head, which has a pronounced roundness in the form of a thickening - the epiphysis of the terminal section, then on the other bone it is associated with it, it is a depression exactly corresponding to it in size and shape, sometimes significant (this in the pelvic bone is called “vinegar” due to its vastness). But there may also be an articulation of one bone head with a structure on the body-diaphysis of another, as is the case in the radioulnar joint.

In addition to the perfect fit of the shapes that form the joint, their surfaces are covered with a thick layer of hyaline cartilage with a literally mirror-smooth surface to glide over each other flawlessly.

But smoothness alone is not enough - the joint should not fall apart into its component parts. Therefore, it is surrounded by a dense elastic connective tissue cuff - a capsule bag, similar to a lady's muff for warming the hands in winter. In addition, it is held together by ligamentous apparatus of varying strength and muscle tone, ensuring biodynamic balance in the system.

A sign of true dysarthrosis is the presence of a full-fledged articular cavity filled with synovial fluid produced by cartilage cells.

The classic and simplest in structure is the shoulder. This is the gap of the joint between its bag and two bone ends that have surfaces: the round head of the humerus and the articular cavity on the scapula that matches it in configuration, filled with synovial fluid, plus ligaments that hold the entire structure together.

Other dysarthroses have a more complex structure - in the wrist, each bone is in contact with several neighboring bones at once.

Spine as a special case

But the relationships between the vertebrae - short-columnar bones with a complex surface topography and many structures for varying degrees of movable adhesion with neighboring formations - are particularly complex.

The spine has a structure reminiscent of a rosary, only its “beads” are the bodies of each of the adjacent bones, which are connected to each other through hemiarthrosis (synchondrosis) based on a cartilaginous disc. Their spinous processes, overlapping each other like tiles, and the arches, forming a container for the spinal cord, are fastened with rigid ligaments.

The joints between the transverse processes of the vertebrae with flat surfaces (as well as the costovertebral ones, formed through the costal heads and articular cavities on the vertebral bodies located laterally) are quite real, having all the necessary attributes: working surfaces, cracks, capsules and ligaments.

In addition to connections with each other and with the ribs, the vertebrae form a fusion in the sacrum area, turning this group into a monolith, to which the “tail”-coccyx is attached through real joints - the formation is quite mobile, especially during childbirth.

Sacroiliac dysarthrosis is the beginning of the pelvic girdle, formed by the bones of the same name, which are closed in a ring by the pubic symphysis in front and in the center.

In addition to the intervertebral joints, there are other joints in the supporting column system: a combination that forms one unpaired and two paired components of the atlanto-axial connection (between the 1st and 2nd vertebrae) and paired atlanto-occipital joints (between the 1st vertebra and the occipital bone).

Due to this very structure, the spine is an incredibly flexible formation, having a large degree of freedom of movement and at the same time extremely strong, bearing the entire weight of the body. In addition to its supporting function, it also plays a protective role, serving as a canal through which the spinal cord passes and is involved in hematopoiesis.

The spectrum of damage to vertebral joints is diverse: from injuries (with various categories of fractures and displacements) to metabolic-dystrophic processes leading to varying degrees of spinal stiffness (osteochondrosis and similar conditions), as well as infectious lesions (in the form of tuberculosis, lues, brucellosis).

Detailed classification

The above classification of bone joints does not include the taxonomy of joints, which has several options.

According to the number of articular surfaces, the following categories are distinguished:

• simple, with two surfaces, as in the joint between the phalanges of the first finger;
• complex when there are more than two surfaces, for example, in the elbow;
• complex with the presence of internal cartilaginous structures dividing the cavity into non-insulated chambers, as in the knee;
• combined in the form of a combination of joints isolated from each other: in the temporomandibular joint, the intraarticular disc divides the working cavity into two separate chambers.

According to the functions performed, joints with one, two and multiple axes of rotation (one-, two- and multi-axial) are distinguished, depending on the shape they look like:

Examples of uniaxial joints are:

• cylindrical – atlantoaxial median;
• trochlear – interphalangeal;
• helical – shoulder-ulnar.

Structures of complex shape:

• ellipsoid, like the radiocarpal lateral;
• condylar, like the knee;
• saddle-shaped, like the metacarpal joint of the first finger.

Multi-axis are represented by varieties:

• spherical, like the shoulder;
• cup-shaped - a deeper variation of spherical (like hip);
• flat (like intervertebral ones).

There is also a separate category of tight joints (amphiarthrosis), differing in the shape of their surfaces, but similar in other respects - they are extremely stiff due to the strong tension of the capsules and a very powerful ligamentous apparatus, therefore their sliding displacement relative to each other is almost imperceptible.

Characteristics, design and functions of the main joints

With all the abundance of joints in the human skeleton, it is most logical to consider them as separate groups - categories of joints:

• skulls;
• spine;
• limb girdles (upper and lower).

Cranial joints

In accordance with this position, the skeleton of the skull includes two diarthrosis:

• temporomandibular;
• atlanto-occipital.

The first of these paired connections is created with the participation of the heads of the lower jaw bone and the working cavities on the temporal bones.

The joint consists of two synchronously functioning formations, although spaced on opposite sides of the skull. According to its configuration, it is condylar and belongs to the category of combined due to the presence of a cartilaginous disc dividing its volume into two chambers isolated from each other.

Thanks to the existence of this diarthrosis, freedom of movement of the lower jaw in three planes is possible and its participation both in the process of primary food processing and in swallowing, breathing and the formation of speech sounds. The jaw also serves as a means of protecting the oral organs from damage and is involved in creating the relief of the face. It can be subject to both injury and infection during the development of acute (mumps) and exacerbation of chronic (tuberculosis, gout) diseases.

The configuration of the paired atlanto-occipital region is also condylar. It serves to connect the skull (its occipital bone with convex working surfaces) with the spine through the first two cervical vertebrae, acting as one, on the first of which - the atlas - there are working fossae. Each half of this synchronously operating formation has its own capsule.

Being biaxial, the atlas allows you to make head movements both according to the frontal and sagittal axes - both nodding and tilting left and right, providing freedom of orientation and the fulfillment of a social role by a person.

The main pathology of atlanto-occipital diarthrosis is injury as a result of a sharp tilting of the head and the development of osteochondrosis and other metabolic-dystrophic conditions due to the long-term preservation of a forced posture.

Shoulder girdle

Considering the description of the spine proposed above, moving on to diarthrosis of the shoulder girdle, it should be understood that the connections the clavicle with the sternum and the scapula with the clavicle are synarthrosis. The real joints are:

• brachial;
• elbow;
• radiocarpal;
• carpometacarpal;
• metacarpophalangeal;
• interphalangeal.

The spherical shape of the head of the humerus is the key to almost complete circular freedom of rotation of the upper limb, therefore the humerus is a multi-axial joint. The second component of the mechanism is the scapular cavity. All other attributes of diarthrosis are also present here. The shoulder joint is most susceptible to damage (due to the large degree of freedom), and to a much lesser extent to infections.

The complex structure of the elbow is due to the articulation of three bones at once: the humerus, radius and ulna, which have a common capsule.

The shoulder-elbow joint is trochlear: the shoulder block enters the notch on the ulna, the humerus-radius is the result of the head of the humeral condyle entering the fossa of the head of the radius bone with the formation of a spherical working area.

Movements in the system are carried out according to two axes: flexion-extension, and also due to the participation of the proximal radioulnar joint, rotation (pronation and supination) is possible, because the head of the radius rolls along the groove on the ulna.

Problems of the elbow joint include damage, as well as inflammatory conditions (with acute and exacerbation of chronic infections), dystrophy due to professional sports.

The distal radioulnar joint is a cylindrical joint that provides vertical rotation of the forearm. In the working cavity there is a disk that separates the said joint from the cavity of the carpal joint.

Diseases of the elbow area:

• arthrosis:
• instability;
• stiffness.

By means of a capsule covering the lower epiphysis of the radius and the first row of carpal bones, an ellipsoidal configuration of the wrist joint is formed. This is a complex articulation with sagittal and frontal axes of rotation, allowing both adduction-abduction of the hand with its circular rotation, and extension-flexion.

The most common diseases:

• damage (in the form of bruises, fractures, sprains, dislocations);
• tenosynovitis;
• synovitis;
• styloiditis;
• varying degrees of severity of tunnel syndrome;
• arthritis and arthrosis;
• osteoarthritis.

The joints of the small bones of the upper limb are combinations of flat and saddle joints (carpometacarpal) with spherical joints (metacarpophalangeal) and block-shaped joints (interphalangeal joints). This design provides strength to the base of the hand, and mobility and flexibility to the fingers.

Pelvic girdle

Diarthrosis of the pelvic girdle includes:

• hip;
• knee;
• ankle;
• tarsometatarsal;
• metatarsophalangeal;
• interphalangeal.

The shape of the multiaxial hip joint is cup-shaped, with the participation of the head of the femur and the ischial cavity, providing adduction and abduction of the hip forward-backward and medially-laterally, as well as its rotation.

TZB is susceptible to damage (due to the high degree of freedom) and damage from microbial flora, most often brought here hematogenously (tuberculosis, brucellosis, gonorrhea).

The most common diseases of the hip area:

• coxarthrosis;
• bursitis;
• tendinitis;
• femoroacetabular impingement syndrome;
• Perthes disease.

The knee joint (trochlear joint) is formed by the participation of the femoral condyles and the concave surface of the tibia. In addition to the powerful ligamentous apparatus, support in the front is created by a sesamoid formation - the patella.

The inner surface is supplemented until it fully matches the articular surfaces with menisci and ligaments. The available movements are flexion-extension and partly rotation.

Pathologies that affect the knee:

• injuries (especially patellar dislocation);
• arthritis;
• arthrosis;
• bursitis;
• knee "mouse".

The creation of the ankle (classical trochlear) joint involves the head-trochlear of the talus and the notch formed by the “fork” of both tibia bones.

The structure of diarthrosis allows you to:

• extension-flexion;
• slight vertical abduction-adduction (in flexion position).

The most common dysfunction is ankle fractures (external or internal), as well as metabolic disorders in the body and blood circulation in the lower extremities.

The tarsal area is formed by a “mosaic” of joints:

• subtalar;
• talocaleonavicular;
• calcaneocuboid;
• wedge-scaphoid.

These are connections of a combined or flat configuration (the first two are cylindrical and spherical).

Metatarsal diarthrosis is represented by various (mostly flat) joints that form a support for the arches of the foot, made by metatarsophalangeal (trochle-shaped) joints.

Also, the block-shaped interphalangeal joints of the feet provide the toes with a sufficient level of mobility and flexibility (patients who have lost both arms draw and even sew with their feet) without sacrificing strength.

Small joints of the feet are characterized by damage due to metabolic-dystrophic processes in the body, with disorders of local and general blood supply and as a result of chronic injuries in the form of wearing high-heeled or simply tight shoes.

The existence of different ways of connecting bones, as well as the diversity of the articular surfaces themselves, understanding their structure and function allows a person not only to live and act, but also to treat the musculoskeletal system (and, if necessary, even replace structures that have become unusable with artificial ones).

Anatomy of the human knee joint and care for it

The knee joint is the largest and most complex in its structure in the human body; its anatomy is extremely complex, because it must not only support the weight of the entire owner’s body, but also allow him to perform a wide variety of movements: from dance steps to the lotus position in yoga.

• Functions
• Connecting components
• Knee muscles
• Innervation and blood supply of the knee

Such a complex structure, an abundance of ligaments, muscles, nerve endings and blood vessels makes the knee very vulnerable to various diseases and injuries. One of the most common causes of disability is injuries to this joint.

It consists of the following formations:

1. bones - femur, tibia and patella,
2. muscles,
3. nerve endings and blood vessels,
4. menisci,
5. cruciate ligaments.

Functions

The knee joint in its structure is close to hinge joints. This allows not only to bend and straighten the lower leg, but also to perform pronation (inward rotation) and supination (outward movement), turning the bones of the lower leg.

Also, when flexing, the ligaments relax, and this makes it possible not only to rotate the lower leg, but also to make rotational and circular movements.

Bone components

The knee joint consists of the femur and tibia, these tubular bones are connected to each other by a system of ligaments and muscles, in addition, in the upper part of the knee there is a rounded bone - the patella or kneecap.

The femur ends in two spherical formations - the femoral condyles and, together with the flat surface of the tibia, form a connection - the tibial plateau.

The patella is attached to the main bones by ligaments and is located in front of the kneecap. Its movements are ensured by sliding along special grooves on the femoral condyles - the pallofemoral recess. All 3 surfaces are covered with a thick layer of cartilage tissue, its thickness reaches 5-6 mm, which provides shock absorption and reduces thorns during movement.

Connecting components

The main ligaments, together with the bones that make up the knee joint, are the cruciate ligaments. In addition to them, on the sides there are lateral collateral ligaments - medial and lateral. Inside there are the most powerful connective tissue formations - the cruciate ligaments. The anterior cruciate ligament connects the femur and the anterior surface of the tibia. It prevents the tibia from moving forward during movement.

The posterior cruciate ligament does the same thing, preventing the tibia from moving posterior to the femur. Ligaments provide connection between bones during movement and help to maintain it; rupture of the ligaments leads to the inability to make voluntary movements and lean on the injured leg.

In addition to the ligaments, the knee joint contains two more connective tissue formations that separate the cartilaginous surfaces of the femur and tibia - the menisci, which are very important for its normal functioning.

Menisci are often called cartilage, but in their structure they are closer to ligaments. Menisci are rounded plates of connective tissue found between the femur and the tibial plateau. They help to correctly distribute the weight of a person’s body, transferring it to a large surface and, in addition, stabilize the entire knee joint.

Their importance for the normal functioning of the joint is easy to understand by looking at the structure of the human knee - the photo makes it possible to see the menisci located between the spherical epiphysis of the femur (lower part) and the flat surface of the tibia.

Knee muscles

The muscles located around the joint and ensuring its functioning can be divided into three main groups:

• anterior muscle group - hip flexors - quadriceps and sartorius muscles,
• posterior group – extensors – biceps, semimembranosus and semitendinosus muscles,
• medial (inner) group - hip adductors - thin and adductor magnus muscles.

• One of the most powerful muscles in the human body is the quadriceps. It is divided into 4 independent muscles, located on the front surface of the femur and attached to the kneecap. There, the muscle tendon turns into a ligament and connects to the tibial tuberosity. The intermedius muscle, one of the branches of the quadriceps muscle, also attaches to the knee capsule and forms the knee muscle. Contraction of this muscle promotes leg extension and hip flexion.
• The sartorius muscle is also part of the muscles of the knee joint. It starts from the anterior iliac axis, crosses the surface of the femur and goes along the inner surface to the knee. There it goes around it from the inside and attaches to the tuberosity of the tibia. This muscle is two-part and therefore participates in flexion of both the thigh and lower leg, as well as in the inward and outward movement of the lower leg.
• Thin muscle - starts from the pubic joint, goes down and attaches to the knee joint. It helps with hip adduction and ankle flexion.

In addition to these muscles, the tendons of the biceps femoris, tendinous, semimembranosus and popliteus muscles pass through the knee joint. They provide adducting and abducting movements of the lower leg. The popliteus muscle is located directly behind the knee and helps with flexion and internal rotation.

Innervation and blood supply of the knee

The knee joint is innervated by branches of the sciatic nerve, which is divided into several parts and innervates the lower leg, foot and knee. The knee joint itself is innervated by the popliteal nerve, it is located behind it, and is divided into the tibial and peroneal branches.

The tibial nerve is located on the back of the leg, and the peroneal nerve is located in front. They provide sensory and motor innervation to the lower leg.

The blood supply to the knee joint is carried out using the popliteal arteries and veins, whose course follows the course of the nerve endings.

What are the risks of injury?

Depending on which component of the knee is damaged, injuries, diseases and pathologies are classified. It can be:

• dislocations,
• fractures of the bones surrounding the joint,
• inflammatory and dystrophic diseases,
• damage to the tissues inside and around the joint, that is, cartilage, capsules, ligaments, as well as adipose tissue.

Comfortable and painless movement in the knee area is possible thanks to the meniscus of the knee joint. It is a cartilage tissue-lining, mainly consisting of collagen fibers (about 70% of the composition). Its main role is to cushion and reduce friction between bone surfaces. For example, when the knee bends, about 80% of the load is taken by the meniscus. Despite its strength, under overload (similar to what professional athletes experience), the meniscus in the knee can be injured, which complicates and limits a person’s mobility. Let's take a closer look at its structure, as well as the diagnosis and prevention of pathologies associated with it.

Structure and functions of the meniscus

The anatomy of the knee joint is quite complex and includes cartilage, menisci (also called crescent cartilages) and cruciate ligaments. The knee joint is not the only one where the meniscus is located: it is also present in the sternoclavicular, acromioclavicular and temporomandibular joints. However, it is the knee meniscus that is most susceptible to injury. It is a triangular cartilaginous formation and is located between the tibia and femur. The structure of cartilage is fibrous, and it itself thickens in the outer part.

How many menisci are there in the knee? In each knee joint there are 2 types:

1. External (lateral). It has a ring-shaped surface. It is more mobile than the medial meniscus, which is why it is less likely to be injured.
2. Internal (medial) meniscus. It is C-shaped and resembles an open ring. In some people it forms a disk shape (see photo for better understanding). Larger in size than the lateral one. The presence of a centrally attached tibial collateral ligament leads to a decrease in its mobility and, as a result, to more injuries.

The meniscus is attached to the capsule of the knee joint, the arteries of which supply it with nutrition (the so-called “red zone”). It is divided into the body, the anterior horn and the posterior horn.

The location and structure of the meniscus is tailored to a number of functions. This is a kind of protective cushion that prevents joints from wearing out and allows them to support body weight, evenly distributing pressure over the joint surface. It performs the following tasks:

• shock absorption when moving;
• joint stabilization;
• distribution of load and reduction of pressure on the joint surface;
• informing the brain about the position of the joint in the form of signals;
• reducing friction between the tibia and femur;
• limitation of the range of motion of the cartilage;
• providing joint lubrication with synovial fluid.

Crescent cartilages have elasticity due to the presence of elastin and special protein compounds in their composition (in total they account for about 30%, the rest is collagen fibers). Strength is due to the ligaments that firmly connect them to the bones. Of the 12 ligaments of the knee joint, the transverse, anterior and posterior meniscofemoral ligaments interact with the meniscus.

Meniscus damage

Damage reduces the mobility of the knee joint, causing discomfort and pain. They can be of the following nature:

1. Degenerative-dystrophic changes. Common to people over 45 years of age and part of the aging process. The fibers begin to gradually deteriorate, tissue nutrition with blood and synovial fluid is reduced, and the structure of the cartilage is weakened. The cause may also be certain diseases (gout, arthritis, rheumatism), metabolic failure, or hypothermia.
2. Traumatic changes. They can occur at any age due to overload. Athletes and manual workers, predominantly male, are primarily at risk. The cause is careless movements such as jumping, spinning or deep squats. This can lead to tears of the outer or inner meniscus, pinching of the outer part of the cartilage pad, and tear of the medial meniscus. In rare cases, the injury is caused directly by a contusion, such as a blow to the knee.

The damage can be isolated, but more often it affects other elements in the knee joint, such as ligaments and joint capsules. You can recognize an injury by the following symptoms:

• increasing pain;
• inability to lean on your leg;
• decreased mobility;
• swelling;
• hematoma (for some types of damage);
• weakness in the upper thigh;
• accumulation of joint fluid;
• clicking in the joint when moving, etc.

Depending on the nature of the lesion, different types of ruptures are distinguished: complete, incomplete, horizontal, combined, radial, with or without displacement. Most often, ruptures of the posterior horn of the internal meniscus are observed.

Interestingly, children under the age of 14 practically do not encounter such injuries: at this age, the cartilage lining is very elastic, which helps to avoid damage.

Diagnosis and treatment

A doctor can diagnose meniscus damage in several ways. Today the following methods are used:

1. Arthroscopy (an invasive method in which a special device is inserted into the joint to see the condition of the meniscus on a monitor).
2. Computed tomography (CT, used primarily to detect damage to bone structures).
3. X-ray.
4. Magnetic resonance imaging (MRI).
5. Palpation.

The methods differ in the accuracy of the data obtained. MRI gives one of the best results: accuracy is more than 85%. The traumatologist chooses the type of diagnosis based on the specific situation; sometimes a combination of them is required.

To solve the problem of the meniscus, in some cases they resort to surgery. Previously, it was practiced to remove it (complete meniscatomy), but now it has been replaced by partial intervention (partial meniscatomy).

A conservative type of treatment is also used, which includes physiotherapy (massage, recreational exercises, some procedures) and the use of chondroprotective drugs.

Knowing what the meniscus is and what important functions it performs allows you to take measures to prevent diseases associated with it.

First of all, these are thoughtful and standardized physical activity, a balanced diet, avoiding hypothermia and sudden careless movements. During active sports, properly selected shoes, bandages and knee pads will help if necessary.