Large human joints. Types and types of human joints

With the presence of a gap between the articulating bones. A joint is a type of articulation of bones; another type of articulation - a continuous connection of bones (without a joint space) - is called synarthrosis. The joints perform both supporting and motor functions.

Rice. 1. The structure of the joint: 1 - articular cartilage; 2 - fibrous membrane of the joint capsule; 3 - ; 4 - joint cavity; 5 - ends of articulating bones (epiphyses); 6 - periosteum.

Rice. 2. Types of hand joints:
1 - ellipsoid;
2 - saddle;
3 - spherical;
4 - blocky.

The main elements of the joint are the articular surfaces (ends) of the connecting bones, articular bags, lined from the inside with a synovial membrane (see), and articular cavities (Fig. 1). In addition to these basic elements that form the joint, there are also auxiliary formations (, disks, menisci and), which are not found in all joints.

The ends of the articulating bones (epiphyses) form the solid foundation of the joint and, due to their structure, can withstand heavy loads. Hyaline cartilage 0.5-2 mm thick, covering the articular surfaces and very firmly connected to the bone, provides a more complete fit of the ends of the bones during movement and acts as a shock absorber in the supporting joints.

The articular bag closes the joint cavity, attaching along the edges of the articular surfaces of the connecting bones. The thickness of this capsule is different. In some joints it is tightly stretched, in others it is free. Two layers are distinguished in the capsule: inner synovial and outer fibrous, consisting of dense. In a number of places, the fibrous layer forms thickenings - ligaments (see). Along with the ligaments that are part of the capsule, extra-articular and intra-articular ligaments also take part in strengthening the joints. Joints are additionally strengthened by passing muscles and their tendons.

The articular cavity in the form of a gap contains a small amount of synovial fluid, which is produced by the synovial membrane and is a transparent yellowish viscous fluid. It serves as a lubrication of the articular surfaces, reducing friction during movements in the joints.

The auxiliary apparatus of the joint, along with ligaments, is represented by intra-articular cartilages (menisci, discs, articular lip), which, located between the articular ends of the bones or along the edge of the joint, increase the contact area of the epiphyses, make them more consistent with each other and play a large role in joint mobility.

The blood supply to the joints occurs due to the branches of the nearest arteries; they form a dense network of anastomoses in the joint capsule. The outflow of blood goes through the veins to the adjacent venous trunks. Lymph outflow is carried out through a network of small lymphatic vessels to the nearest lymphatic collectors.

The innervation of the joints is provided by the spinal and sympathetic nerves.

The function of the joints is determined mainly by the shape of the articulating surfaces of the epiphyses of the bones. The articular surface of one bone is, as it were, an imprint of another, in most cases one surface is convex - the articular head, and the other is concave - the articular cavity. These surfaces do not always fully correspond to each other, often the head has a greater curvature and vastness than the cavity.

If two bones take part in the formation of the joint, then such a joint is called simple; if more bones - difficult.

The shape of the articular surfaces of the bones is compared with geometric figures and, accordingly, the joints are distinguished: spherical, ellipsoid, block-shaped, saddle-shaped, cylindrical, etc. Movements can be carried out around one, two and three axes, forming one- (cylindrical and block-shaped), two- (ellipsoid and saddle) and multiaxial (spherical) joints (Fig. 2). The number and position of the axes determine the nature of the movements. There are movements around the frontal axis - flexion and extension, sagittal axis - adduction and abduction, longitudinal axis - rotation and multi-axial rotational movement.

Joints can be classified according to the following principles:
1) by the number of articular surfaces,
2) according to the shape of the articular surfaces and
3) by function.

According to the number of joints surfaces are:
1. Simple joint (art. simplex) having only 2 articular surfaces, such as interphalangeal joints.
2. Complex joint (art. composite) having more than two articular surfaces, such as the elbow joint. A complex joint consists of several simple joints in which movements can be performed separately. The presence of several joints 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 (two-chamber joint). The division into chambers occurs either completely if the intra-articular cartilage is disc-shaped (for example, in the temporomandibular joint), or incompletely if the cartilage takes the form of a semilunar meniscus (for example, in the knee joint).
4. Combined joint represents a combination of several joints isolated from each other, located separately from each other, but functioning together. Such, for example, are both temporomandibular joints, the proximal and distal radioulnar joints, etc.
Since the combined joint is a functional combination of two or more anatomically separate joints, in this way it differs from the complex and complex joints, each of which, being anatomically unified, is composed of functionally different compounds.

Form and function classification is carried out as follows.
Joint function determined by the number of axes around which movements are made. The number of axes around which movements occur in a given joint depends on the shape of its articular surfaces. So, for example, the cylindrical shape of the joint allows movement only around one axis of rotation.
In this case, the direction of this axis will coincide with the axis of the cylinder itself: if the cylindrical head is vertical, then the movement is performed around the vertical axis (cylindrical joint); if the cylindrical head lies horizontally, then the movement will take place around one of the horizontal axes coinciding with the axis of the head, for example, the frontal (block joint).

In contrast to this spherical shape and the head makes it possible to rotate around a plurality of axes coinciding with the radii of the ball (spherical joint).
Therefore, between the number of axles and form articular surfaces there is a complete correspondence: 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.

The figure shows:
Uniaxial joints: 1a - block-shaped talocrural joint (articulario talocruralis ginglymus)
1b - block-shaped interphalangeal joint of the hand (articulatio interpalangea manus ginglymus);
1c - cylindrical shoulder-radial joint of the elbow joint, articulatio radioulnaris proximalis trochoidea.

Biaxial joints: 2a - elliptical wrist joint, articulatio radiocarpea ellipsoidea;
2b - condylar knee joint (articulatio genus -articulatio condylaris);
2c - saddle carpometacarpal joint, (articulatio carpometacarpea pollicis - articulatio sellaris).

Triaxial joints: 3a - spherical shoulder joint (articulatio humeri - articulatio spheroidea);
3b - cup-shaped hip joint (articulatio coxae - articulatio cotylica);
3c - flat sacroiliac joint (articulatio sacroiliaca - articulatio plana).

I. Uniaxial joints

1. Cylindrical joint, art. trochoidea. The 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 rotational.

2. Block joint, ginglymus(example - interphalangeal joints of the fingers). Its block-shaped 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). Guiding groove and scallop on the articulating surfaces eliminate the possibility of lateral slip and promote movement around one axis.
If the guide groove block is located not perpendicular to the axis of the latter, but at a certain angle to it, then when it is continued, a helical line is obtained. Such a block-shaped joint is considered as a helical joint (an example is the glenohumeral joint). The movement in the helical joint is the same as in the purely trochlear joint.
According to the rules of location ligamentous apparatus, in the cylindrical joint, the guide ligaments will be located perpendicular to the vertical axis of rotation, in the 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.

II. 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 respectively 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.
Bundles in elliptical joints located perpendicular to the axes of rotation, at their ends.

2. condylar joint, articulatio condylaris(example - knee joint).
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.

condylar joint can be considered as a kind of elliptical, representing a transitional form from a block-shaped joint to an elliptical one. Therefore, its main axis of rotation will be frontal.

From blocky condylar joint differs in that there is a large difference in size and shape between the articulating surfaces. As a result, in contrast to the block-like joint, movements around two axes are possible in the condylar joint.

From elliptical joint it differs in the number of articular heads. Condylar joints always have two condyles, located more or less sagittally, which are either in the same capsule (for example, the two condyles of the femur involved in the knee joint), or are located in different articular capsules, as in the atlantooccipital articulation.

Because the in the condylar joint of the head do not have the correct ellipse configuration, the second axis will not necessarily be horizontal, as is typical for a typical elliptical joint; it can also be vertical (knee joint).

If a condyles are located in different articular capsules, then such a condylar joint is close in function to an elliptical joint (atlantooccipital articulation). If the condyles are close together and are 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 block joint.

3. saddle joint, art. sellaris(an example is the carpometacarpal joint of the first finger).
This joint is formed by 2 saddle articular surfaces, sitting "on top" of each other, of which one moves along and across the other. Due to this, movements are made in it around two mutually perpendicular axes: frontal (flexion and extension) and sagittal (abduction and adduction).
In biaxial joints it is also possible to move from one axis to another, i.e., circular motion (circumductio).

III. Multiaxial joints

1. spherical. ball 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 be performed around many axes corresponding to the radii of the ball, but in practice, three main axes are usually distinguished among them, perpendicular to each other and intersecting at the center of the head:
1) transverse (frontal), around which flexion occurs, flexio, when the moving part forms an angle with the frontal plane, open anteriorly, and extension, extensio, when the angle is open backwards;
2) anteroposterior (sagittal), around which abduction, abductio, and adduction, adductio, are performed;
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.

ball joint- the most free 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. There are few auxiliary ligaments in typical spherical joints, which determines the freedom of their movements.

Variety spherical joint- bowl joint, art. cotylica (cotyle, Greek - bowl). Its articular cavity is deep and covers most of the head. As a result, movements in such a joint are less free than in a typical spherical joint; we have a sample of the bowl-shaped joint in the hip joint, where such a device contributes to greater stability of the joint.

A - uniaxial joints: 1.2 - block joints; 3 - cylindrical joint;
B - biaxial joints: 4 - elliptical joint: 5 - we are a silk joint; 6 - saddle joint;
B - triaxial joints: 7 - spherical joint; 8- bowl-shaped joint; 9 - flat 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, therefore, movements in them are performed around all three axes, but the range of movements due to the insignificant difference in the areas of the articular surfaces is small.
Bundles in multi-axle joints located on all sides of the joint.

Tight joints - amphiarthrosis

Under this name, a group of joints with different the shape of the articular surfaces, but similar in other ways: they have a short, tightly stretched joint capsule and a very strong, non-stretching auxiliary apparatus, in particular short reinforcing ligaments (an example is the sacroiliac joint).

As a result, the articular surfaces are in close contact with each other. friend which severely restricts movement. Such inactive joints are called tight joints - amphiarthrosis (BNA). Tight joints soften shocks and tremors 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 of a sliding nature and are extremely insignificant.

A - triaxial (multiaxial) joints: A1 - spherical joint; A2 - flat joint;
B - biaxial joints: B1 - elliptical joint; B2 - saddle joint;
B - uniaxial joints: B1 - cylindrical joint; B2 - block joint

Video lesson: Classification of joints. Range of motion in the joints

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Joints unite the bones of the skeleton into a single whole. More than 180 different joints help a person move. Together with bones and ligaments, they are referred to as the passive part of the motor apparatus.

Joints can be compared to hinges, the task of which is to ensure smooth sliding of bones relative to each other. In their absence, the bones will simply rub against each other, gradually breaking down, which is a very painful and dangerous process. In the human body, the joints play a triple role: they help maintain the position of the body, participate in the movement of body parts relative to each other, and are organs of locomotion (movement) of the body in space.

Each joint has various elements that facilitate the mobility of some parts of the skeleton and ensure strong conjugation of others. In addition, there are non-osseous tissues that protect the joint and soften interosseous friction. The structure of the joint is very interesting.

The main elements of the joint:

joint cavity;

Epiphyses of the bones that form the joint. The epiphysis is a rounded, often expanded, terminal section of a tubular bone that forms a joint with an adjacent bone by articulating their articular surfaces. One of the articular surfaces is usually convex (located on the articular head), and the other is concave (formed by the articular fossa)

Cartilage is the tissue that covers the ends of bones and cushions their friction.

The synovial layer is a kind of bag that lines the inner surface of the joint and secretes synovium, a fluid that nourishes and lubricates the cartilage, since the joints do not have blood vessels.

The joint capsule is a sleeve-like, fibrous layer enveloping the joint. It gives the bones stability and prevents their excessive displacement.

The menisci are two hard cartilages shaped like crescents. They increase the area of contact between the surfaces of two bones, as, for example, the knee joint.

Ligaments are fibrous formations that strengthen interosseous joints and limit the amplitude of bone movement. They are located on the outside of the joint capsule, but in some joints they are located inside for better strength, such as round ligaments in the hip joint.

The joint is an amazing natural mechanism of movable conjugation of bones, where the ends of the bones are connected in the articular bag. bag outside is a fairly strong fibrous tissue - it is a dense protective capsule with ligaments that help control and hold the joint, preventing displacement. From the inside, the articular bag is synovial membrane.

This membrane produces synovial fluid - lubrication of the joint, viscoelastic consistency, which even in a healthy person is not so much, but it occupies the entire joint cavity and is able to perform important functions:

1. It is a natural lubricant that gives the joint freedom and ease of movement.

2. It reduces the friction of the bones in the joint, and thus protects the cartilage from abrasion and wear.

3. Acts as shock absorber and shock absorber.

4. Works as a filter, providing and maintaining cartilage nutrition, while protecting it and the synovial membrane from inflammatory factors.

synovial fluid A healthy joint has all of these properties, largely due to hyaluronic acid found in the synovial fluid, as well as in cartilage tissue. It is this substance that helps your joints to fully perform their functions and allows you to lead an active life.

If the joint is inflamed or diseased, then more synovial fluid is produced in the synovial membrane of the joint capsule, which also contains inflammatory agents that increase swelling, swelling, and pain. Biological inflammatory agents destroy the internal structures of the joint.

The ends of the joints of the bones are covered with an elastic thin layer of smooth substance - hyaline cartilage. Articular cartilage does not contain blood vessels or nerve endings. The cartilage, as has been said, receives its nourishment from the synovial fluid and from the bony structure beneath the cartilage itself, the subchondral bone.

Cartilage basically performs the function of a shock absorber - it reduces pressure on the mating surfaces of the bones and ensures smooth sliding of the bones relative to each other.

Functions of cartilage

1. Reduce friction between joint surfaces

2. Absorb shocks transmitted to the bone during movement

Cartilage is made up of special cartilage cells - chondrocytes and intercellular substance matrix. The matrix consists of loosely located connective tissue fibers - the main substance of cartilage, which is formed by special compounds - glycosaminoglycans.
Namely, connected by protein bonds, glycosaminoglycans that form larger cartilage structures - proteoglycans - are the best natural shock absorbers, since they have the ability to restore their original shape after mechanical compression.

Due to the special structure, the cartilage resembles a sponge - absorbing fluid in a calm state, it releases it into the articular cavity under load and thus, as it were, additionally "lubricates" the joint.

Such a common disease as arthrosis upsets the balance between the formation of new and the destruction of the old building material that forms cartilage. Cartilage (the structure of the joint) changes from strong and elastic to dry, thin, dull and rough. The underlying bone thickens, becomes more uneven, and begins to grow away from the cartilage. This contributes to the restriction of movement and causes deformation of the joints. There is a seal of the joint capsule, as well as its inflammation. The inflammatory fluid fills the joint and begins to stretch the capsule and joint ligaments. This creates a painful feeling of stiffness. Visually, you can observe an increase in the joint in volume. Pain, and subsequently deformation of the surfaces of the joints in arthrosis, leads to tight joint mobility.

Joints are distinguished by the number of articular surfaces:

simple joint (lat. articulatio simplex) - has two articular surfaces, for example, the interphalangeal joint of the thumb;
complex joint (lat. articulatio composita) - has more than two articular surfaces, for example, the elbow joint;
complex joint (lat. articulatio complexa) - contains intra-articular cartilage (meniscus or disc), dividing the joint into two chambers, for example, the knee joint;
combined joint - a combination of several isolated joints located separately from each other, for example, the temporomandibular joint.

Joints with movement

. shoulder joint: the articulation that provides the greatest amplitude of movements of the human body is the articulation of the humerus with the scapula using the glenoid cavity of the scapula.

. elbow joint: connection of the humerus, ulna and radius bones, allowing you to make a rotational movement of the elbow.

. Knee-joint: a complex joint that provides flexion and extension of the leg and rotational movements. The femur and tibia are articulated at the knee joint - the two longest and strongest bones, which, together with the patella, located in one of the tendons of the quadriceps muscle, are pressed by almost the entire weight of the skeleton.

. hip joint: connection of the femur with the bones of the pelvis.

. wrist joint: formed by several joints located between numerous small flat bones connected by strong ligaments.

. Ankle joint: the role of ligaments is very important in it, which not only provide movement of the lower leg and foot, but also support the concavity of the foot.

There are the following main types of movements in the joints:

movement around the frontal axis - flexion and extension;
movements around the sagittal axis - adduction and abduction of movement around the vertical axis, that is, rotation: inwards (pronation) and outwards (supination).

The human hand contains: 27 bones, 29 joints, 123 ligaments, 48 nerves and 30 named arteries. Throughout life, we move our fingers millions of times. The movement of the hand and fingers is provided by 34 muscles, only when moving the thumb, 9 different muscles are involved.

shoulder joint

It is the most mobile in humans and is formed by the head of the humerus and the glenoid cavity of the scapula.

The articular surface of the scapula is surrounded by a ring of fibrous cartilage - the so-called articular lip. The tendon of the long head of the biceps brachii passes through the joint cavity. The shoulder joint is strengthened by a powerful coraco-shoulder ligament and the surrounding muscles - deltoid, subscapular, supra- and infraspinatus, large and small round. The pectoralis major and latissimus dorsi muscles also take part in the movements of the shoulder.

The synovial membrane of the thin articular capsule forms 2 extra-articular torsion - the tendons of the biceps of the shoulder and the subscapularis. The anterior and posterior arteries enveloping the humerus and the thoracoacromial artery take part in the blood supply of this joint, the venous outflow is carried out into the axillary vein. The outflow of lymph occurs in the lymph nodes of the armpit. The shoulder joint is innervated by branches of the axillary nerve.

In the shoulder joint, movements around 3 axes are possible. Flexion is limited by the acromial and coracoid processes of the scapula, as well as the coracobrachial ligament, extension by the acromion, coracobrachial ligament, and joint capsule. Abduction in the joint is possible up to 90°, and with the participation of the girdle of the upper extremities (with the inclusion of the sternoclavicular joint) - up to 180°. The abduction stops at the moment the large tubercle of the humerus abuts against the coracoid-acromial ligament. The spherical shape of the articular surface allows a person to raise the arm, take it back, rotate the shoulder together with the forearm, the hand in and out. This variety of hand movements was a decisive step in the process of human evolution. The shoulder girdle and shoulder joint in most cases function as a single functional entity.

hip joint

It is the most powerful and heavily loaded joint in the human body and is formed by the acetabulum of the pelvic bone and the head of the femur. The hip joint is strengthened by the intra-articular ligament of the head of the femoral brush, as well as the transverse ligament acetabulum, covering the neck of the femur. Outside, a powerful ilio-femoral, pubic-femoral and ischio-femoral ligaments are woven into the capsule.

The blood supply to this joint is carried out through the arteries that envelop the femur, branches of the obturator and (inconsistently) branches of the superior perforating, gluteal and internal pudendal arteries. The outflow of blood occurs through the veins surrounding the femur, into the femoral vein and through the obturator veins into the iliac vein. Lymph drainage is carried out to the lymph nodes located around the external and internal iliac vessels. The hip joint is innervated by the femoral, obturator, sciatic, superior and inferior gluteal, and pudendal nerves.
The hip joint is a type of ball-and-socket joint. It allows movement around the frontal axis (flexion and extension), around the sagittal axis (abduction and adduction) and around the vertical axis (external and internal rotation).

This joint is under heavy load, so it is not surprising that its lesions occupy the first place in the general pathology of the articular apparatus.

Knee-joint

One of the largest and most complex human joints. It is made up of 3 bones: the femur, tibia, and fibula. Stability of the knee joint is provided by intra- and extra-articular ligaments. The extra-articular ligaments of the joint are the peroneal and tibial collateral ligaments, the oblique and arcuate popliteal ligaments, the patellar ligament, and the medial and lateral patella ligaments. The intraarticular ligaments include the anterior and posterior cruciate ligaments.

The joint has many auxiliary elements, such as menisci, intra-articular ligaments, synovial folds, synovial bags. Each knee joint has two menisci, one external and one internal. The menisci have the form of crescents and perform a shock-absorbing role. The auxiliary elements of this joint include synovial folds, which are formed by the synovial membrane of the capsule. The knee joint also has several synovial bags, some of which communicate with the joint cavity.

Everyone had to admire the performances of gymnasts and circus performers. People who can climb into small boxes and bend unnaturally are said to have gutta-percha joints. Of course, this is not so. The authors of The Oxford Handbook of Body Organs assure readers that "in such people the joints are phenomenally flexible" - in medicine this is called joint hypermobility syndrome.

The shape of the joint is a condylar joint. It allows movements around 2 axes: frontal and vertical (with a bent position in the joint). Flexion and extension occur around the frontal axis, and rotation occurs around the vertical axis.

The knee joint is very important for human movement. With each step, by bending, it allows the foot to step forward without hitting the ground. Otherwise, the leg would be brought forward by raising the hip.

According to the World Health Organization, every 7th inhabitant of the planet suffers from joint pain. Between the ages of 40 and 70, joint disease occurs in 50% of people and in 90% of people over 70 years of age.
According to www.rusmedserver.ru, meddoc.com.ua

Joint represents a discontinuous, cavitary, movable connection, or articulation, articulatio synovialis (Greek arthron - joint, hence arthritis - inflammation of the joint).

In each joint, the articular surfaces of the articulating bones, the articular capsule surrounding the articular ends of the bones in the form of a clutch, and the articular cavity located inside the capsule between the bones are distinguished.

Articular surfaces, facies articulares, covered with articular cartilage, cartilago articularis, hyaline, less often fibrous, 0.2-0.5 mm thick. Due to constant friction, the articular cartilage acquires a smoothness that facilitates the sliding of the articular surfaces, and due to the elasticity of the cartilage, it softens shocks and serves as a buffer. Articular surfaces usually more or less correspond to each other (congruent). So, if the articular surface of one bone is convex (the so-called articular head), then the surface of the other bone is correspondingly concave (articular cavity).

Articular capsule, capsula articularis, surrounding the hermetically articular cavity, adheres to the articulating bones along the edge of their articular surfaces or slightly retreating from them. It consists of an outer fibrous membrane, membrana fibrosa, and an inner synovial membrane, membrana synovialis.

The synovial membrane is covered on the side facing the articular cavity with a layer of endothelial cells, as a result of which it has a smooth and shiny appearance. It secretes into the joint cavity a sticky transparent synovial fluid - synovia, synovia, the presence of which reduces the friction of the articular surfaces. The synovial membrane ends at the edges of the articular cartilage. It often forms small processes called synovial villi, villi synovidles. In addition, in some places it forms synovial folds, sometimes larger, sometimes smaller, plicae synovidles, moving into the joint cavity. Sometimes synovial folds contain a significant amount of fat growing into them from the outside, then the so-called fat folds, plicae adiposae, are obtained, an example of which is the plicae alares of the knee joint. Sometimes in the thinned places of the capsule, bag-like protrusions or eversion of the synovial membrane are formed - synovial bags, bursae synovidles, located around the tendons or under the muscles lying near the joint. Being filled with synovium, these synovial bags reduce the friction of the tendons and muscles during movement.

Articular cavity, cavitas articularis, represents a hermetically closed slit-like space, limited by the articular surfaces and the synovial membrane. Normally, it is not a free cavity, but is filled with synovial fluid, which moisturizes and lubricates the articular surfaces, reducing friction between them. In addition, synovia plays a role in fluid exchange and in strengthening the joint due to the adhesion of surfaces. It also serves as a buffer that softens the pressure and shocks of the articular surfaces, since the movement in the joints is not only sliding, but also the divergence of the articular surfaces. Between the articular surfaces there is a negative pressure (less than atmospheric pressure). Therefore, their divergence is prevented by atmospheric pressure. (This explains the sensitivity of the joints to fluctuations in atmospheric pressure in certain diseases of them, because of which such patients can predict worsening weather.)

If the joint capsule is damaged, air enters the joint cavity, as a result of which the articular surfaces immediately diverge. Under normal conditions, the divergence of the articular surfaces, in addition to negative pressure in the cavity, is also prevented by ligaments (intra- and extra-articular) and muscles with sesamoid bones embedded in the thickness of their tendons.

Ligaments and tendons of the muscles make up the auxiliary strengthening apparatus of the joint. In a number of joints there are additional devices that complement the articular surfaces - intra-articular cartilage; they consist of fibrous cartilaginous tissue and have the appearance of either solid cartilaginous plates - disks, disci articulares, or non-continuous, crescent-shaped formations and therefore called menisci, menisci articulares (meniscus, lat. - crescent), or in the form of cartilaginous rims, labra articularia (articular lips). All these intra-articular cartilages fuse along their circumference with the articular capsule. They arise as a result of new functional requirements as a response to the complication and increase in static and dynamic loads. They develop from the cartilage of the primary continuous joints and combine strength and elasticity, resisting shock and facilitating movement in the joints.

Biomechanics of joints. In the body of a living person, joints play a triple role:

they help to maintain the position of the body;
participate in the movement of body parts in relation to each other and
are organs of locomotion (movement) of the body in space.

Since in the process of evolution the conditions for muscular activity were different, joints of various forms and functions were obtained.

In terms of 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 around three or more axes. In the joints, movements are made around three main axes.

There are the following types of movements in the joints:

Movement around the frontal (horizontal) axis - flexion (flexio), i.e., a decrease in the angle between the articulating bones, and extension (extensio), i.e., an increase in 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): inwards (pronatio) and outwards (supinatio).
Circular motion (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 shape of a cone.

Gliding movements of the articular surfaces are also possible, as well as their removal from each other, as, for example, is observed when stretching the fingers. The nature of movement in the joints is determined by the shape of the articular surfaces. The range of motion in the joints depends on the difference in the size of the articulating surfaces. If, for example, the articular fossa represents an arc of 140° along its length, and the head of 210°, then the arc of motion 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 also be limited by various kinds of brakes, the role of which is performed by certain ligaments, muscles, bone protrusions, etc. Since increased physical (power) load, which causes working hypertrophy of bones, ligaments and muscles , leads to the growth of these formations and limitation of mobility, then different athletes have different flexibility in the joints depending on the sport. For example, the shoulder joint has more range of motion in track and field athletes and less in weightlifters.

If the decelerating devices in the joints are especially strongly developed, then the movements in them are sharply limited. Such joints are called tight. The amount of movement is also influenced by intra-articular cartilage, which increases the variety of movements. So, in the temporomandibular joint, which, according to the shape of the articular surfaces, belongs to biaxial joints, due to the presence of an intraarticular disk, three kinds of movements are possible.

The classification of joints can be carried out according to the following principles:

according to the number of articular surfaces,
the shape of the articular surfaces and
by function.

According to the number of articular surfaces, there are:

Simple joint (art. simplex) having only 2 articular surfaces, such as interphalangeal joints.
Complex joint (art. composite) having more than two articular surfaces, such as the elbow joint. A complex joint consists of several simple joints in which movements can be performed separately. The presence of several joints in a complex joint determines the commonality of their ligaments.
Complex joint (art. complexa) containing intra-articular cartilage, which divides the joint into two chambers (two-chamber joint). The division into chambers occurs either completely if the intra-articular cartilage is disc-shaped (for example, in the temporomandibular joint), or incompletely if the cartilage takes the form of a semilunar meniscus (for example, in the knee joint).
Combined joint represents a combination of several joints isolated from each other, located separately from each other, but functioning together. Such, for example, are both temporomandibular joints, the proximal and distal radioulnar joints, etc. Since the combined joint is a functional combination of two or more anatomically separate joints, this distinguishes it from the complex and complex joints, each of which, being anatomically single, composed of functionally different compounds.

In form and function classification is carried out as follows.

The function of the joint is determined by the number of axes around which movements are made. The number of axes around which movements occur in a given joint depends on the shape of its articular surfaces. So, for example, the cylindrical shape of the joint allows movement only around one axis of rotation. In this case, the direction of this axis will coincide with the axis of the cylinder itself: if the cylindrical head is vertical, then the movement is performed around the vertical axis (cylindrical joint); if the cylindrical head lies horizontally, then the movement will take place around one of the horizontal axes coinciding with the axis of the head, for example, the frontal (block joint). In contrast, the spherical shape of the head makes it possible to rotate around a plurality of axes coinciding with the radii of the ball (spherical joint). Consequently, there is a 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).

It is possible to outline the following unified anatomical and physiological classification of joints.

Uniaxial joints.

Cylindrical joint, art. trochoidea. The 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 rotational.

Block joint, ginglymus(example - interphalangeal joints of the fingers). Its block-shaped 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). Guiding groove and scallop on the articulating surfaces eliminate the possibility of lateral slip and promote movement around one axis.

If the guide groove of the block is not located perpendicular to the axis of the latter, but at a certain angle to it, then when it continues, a helical line is obtained. Such a block-shaped joint is considered as a helical joint (an example is the glenohumeral joint). The movement in the helical joint is the same as in the purely trochlear joint. According to the laws of the location of the ligamentous apparatus, in the cylindrical joint, the guide ligaments will be located perpendicular to the vertical axis of rotation, in the 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.

Ellipsoid joint, articuldtio 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 respectively 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.

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 as a kind of elliptical joint, representing a transitional form from the block joint to the elliptical joint. Therefore, its main axis of rotation will be frontal. 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 block-like joint, movements around two axes are possible in the condylar joint. It differs from the elliptical joint in the number of articular heads.

Condylar joints always have two condyles, located more or less sagittally, which are either in the same capsule (for example, the two condyles of the femur involved in the knee joint), or are located in different articular capsules, as in the atlantooccipital articulation. Since the heads do not have the correct elliptical configuration in the condylar joint, the second axis will not necessarily be horizontal, as is typical for a typical elliptical 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 an elliptical joint (atlantooccipital articulation). If the condyles are close together and are 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 block joint.

Saddle joint, art. selldris(an example is the carpometacarpal joint of the first finger). This joint is formed by 2 saddle-shaped articular surfaces, sitting "on top" of each other, of which one moves along and across the other. Due to this, movements are made in it around two mutually perpendicular axes: frontal (flexion and extension) and sagittal (abduction and adduction). In biaxial joints, it is also possible to move from one axis to another, i.e., circular motion (circumductio).

Multiaxial joints.

Spherical. Ball joint, art. spheroidea (an example is the shoulder joint). One of the articular surfaces forms a convex, spherical head, the other - a correspondingly concave articular cavity.

Theoretically, movement can be performed around many axes corresponding to the radii of the ball, but in practice, three main axes are usually distinguished among them, perpendicular to each other and intersecting at the center of the head:

transverse (frontal), around which flexion occurs, flexio, when the moving part forms an angle with the frontal plane, open anteriorly, and extension, extensio, when the angle is open backwards;
anteroposterior (sagittal), around which abduction, abductio, and adduction, adductio, are performed;
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 joint is the freest 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. There are few auxiliary ligaments in typical spherical joints, which determines the freedom of their movements.

A kind of spherical joint - cup joint, art. cotylica (cotyle, Greek - bowl). Its articular cavity is deep and covers most of the head. As a result, movements in such a joint are less free than in a typical spherical joint; we have a sample of the bowl-shaped joint in the hip joint, where such a device contributes to greater stability of the joint.

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, therefore, movements in them are performed around all three axes, but the range of movements due to the insignificant difference in the areas of the articular surfaces is small. Ligaments in multiaxial joints are located on all sides of the joint.

Tight joints - amphiarthrosis. Under this name, a group of joints with a different shape of the articular surfaces, but similar in other ways, is distinguished: they have a short, tightly stretched joint capsule and a very strong, non-stretching auxiliary apparatus, in particular short reinforcing ligaments (an example is 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 tremors 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 of a sliding nature and are extremely insignificant.

GENERAL INFORMATION

Arthrology is a branch of anatomy that studies the joints of bones. According to the development, structure and function, all bone joints can be divided into 2 large groups: continuous and intermittent. Continuous connections (synarthrosis) are formed by various types of connective tissue. Intermittent joints (diarrhosis) are characterized by the presence of a cavity between the articulating surfaces of the bones.

Depending on the type of tissue connecting the bones, there are three types of continuous connections.

1. Syndesmosis, syndesmosis, is a type of continuous connection of bones through connective tissue. Syndesmoses include ligaments, interosseous membranes, sutures, fontanelles, gomphosis. Fibrous ligaments, ligamenta, are fibrous bundles of connective tissue. Between the arches of the vertebrae, the ligaments consist of elastic connective tissue (synelastosis), these are yellow ligaments, ligament flava.

Interosseous membranes, membrana interossea, is a connective tissue that fills large gaps between bones, for example, between the bones of the forearm and lower leg.

The sutures, suturae, are connective tissue that takes on the character of a thin layer between the bones of the skull.

According to the shape of the connecting bone edges, the following seams are distinguished:

A) dentate, sutura serrata, between the frontal and parietal bones, the parietal and occipital bones of the skull.

B) scaly, sutura squamosa, between the edges of the temporal and parietal bones.

C) flat, sutura plana, between the bones of the facial skull.

Fontanelles, fonticuli, are non-ossified connective tissue areas of the cranial vault of a newborn.

Impaction, gomfosis, is the connection of the tooth with the bone tissue of the dental alveolus.

2. Cartilaginous connections, synchondrosis, synchondrosis, these are continuous connections of bones through cartilaginous tissue. Synchondroses are temporary and permanent.

Temporary synchondroses include epiphyseal cartilages connecting the diaphysis and epiphyses of tubular bones; cartilage between the sacral vertebrae. Temporary synchondrosis persists in childhood, and then is replaced by a bone connection - synostosis.

Permanent synchondrosis is present between the 1st rib and the manubrium of the sternum. If a narrow gap is formed in the center of synchondrosis, which does not have the character of an articular cavity with articular surfaces and a capsule, then such a connection becomes transitional from continuous to intermittent and is called symphysis, symphysis, for example, pubic symphysis, symphysis pubica.

3. Bone connections, synostoses, synostosis, is formed as a result of the replacement of temporary cartilage with bone tissue or at the site of syndesmosis, for example, during ossification of the sutures between the bones of the skull in old age.

Intermittent, or synovial, connections. These include joints, articulatio. These connections have a more complex structure and, unlike sedentary or completely immobile continuous connections, make possible a variety of movements of parts of the human body.

The joint, articulatio, is an organ in which the main and auxiliary elements are distinguished.

The main elements of the joint:

Articular surfaces, facies articularis, are located on the bones at the points of their articulation with each other. In most joints, one of the articulating surfaces is convex - the articular head, and the other is concave - the articular cavity.

Articular cartilage, cartilage articularis, covers the articular surfaces. Most articular surfaces are covered with hyaline cartilage, and only a few joints, such as the temporomandibular and sternoclavicular, have fibrous cartilage.

Due to its elasticity, the articular cartilage protects the ends of the bones from damage during shocks and concussions.

The articular capsule, capsula articularis, surrounds the parts of the bones that articulate with each other and hermetically closes the joint. In the joint capsule, there are: a) an outer fibrous membrane built from dense fibrous connective tissue; b) the inner synovial membrane, which produces intra-articular fluid - synovia.

The articular cavity, cavitas articularis, is a slit-like space between the articular surfaces, which contains the synovium.

Synovia is a viscous fluid that is found in the joint cavity. Synovia wets the articular surfaces, reducing friction during joint movements, provides nutrition to the articular cartilage and metabolism in the joint.

Auxiliary elements of the joint:

The articular disc, discus articularis, is a cartilaginous plate located between the articular surfaces and dividing the articular cavity into two chambers.

Articular menisci, menisci articularis, are curved cartilaginous plates located in the cavity of the knee joint between the condyles of the femur and tibia. The articular discs and menisci increase the contact area of the articular surfaces and are shock absorbers, and also play a role in movements.

The articular lip, labrum articulare, is a cartilaginous rim that is attached along the edge of the articular cavity and increases its area and, consequently, the contact area of the articular surfaces.

Ligaments, ligamenta, - form the ligamentous apparatus of the joint, apparatus ligamentosus. Ligaments strengthen the joint, inhibit movement, and may also direct movement.

Distinguish: a) extracapsular ligaments separated from the joint capsule by connective tissue; b) capsular ligaments woven into the joint capsule; c) intracapsular ligaments located in the joint cavity and covered with a synovial membrane.

Joint classification

The joints of the human body are very diverse in their structure and function. Classification of joints by structure:

A simple joint, articulatio simplex, is formed by two bones, for example, interphalangeal joints.

A compound joint, articulatio composita, is formed by 3 or more bones, for example, the elbow joint, ankle joint.

A complex joint, articulatio complexa, is a joint in which there is a disc or menisci, for example, the knee joint, sternoclavicular joint.

A combined joint, articulatio combinata, is a combination of several joints isolated from each other, but functioning together, for example, the temporomandibular joints, the proximal and distal radioulnar joints.

According to the shape of the articular surfaces, the joints are spherical, bowl-shaped, flat, ellipsoid, saddle, condylar, block-shaped and rotational (cylindrical).

Joint movements are possible around the frontal, sagittal and vertical axes. 1) Movement around the frontal axis is defined as flexion, flexio, and extension, extensio. 2) Around the sagittal axis - abduction, abductio, and adduction, adductio. 3) Around the vertical axis of movement is called rotation, rotatio; Distinguish between outward rotation - supination, supinatio, and inward rotation - pronation, pronatio. Circumduction, circumductio, is a circular movement, the transition from one axis to another. According to the number of axes of motion, the joints are uniaxial, biaxial and multiaxial. Multiaxial are spherical and cup-shaped joints. A typical spherical joint is the shoulder joint, in which movements are possible around 3 axes - frontal (flexion and extension), sagittal (abduction and adduction) and vertical (outward and inward rotation). The hip joint has a bowl shape - it differs from the spherical joint in a deeper articular cavity. In flat joints, movements are sliding in different directions. Ellipsoid, condylar and saddle joints have 2 axes of movement: flexion and extension occur around the frontal axis, and adduction and abduction around the sagittal axis. Block and rotational joints have one axis of rotation. In the block joint, movements occur around the frontal axis - flexion and extension. In a cylindrical joint, movement occurs around a vertical axis - rotation.

On a functional basis, combined joints are distinguished, articulations combinatae; - these are 2 or more joints that are anatomically separate (that is, they have separate capsules), but participate in movements together. For example, two temporomandibular joints, the proximal radioulnar and distal radioulnar joints.

Classification of joints according to form and function

Uniaxial joints

Biaxial joints

Condylar, art. condylaris	Frontal, sagittal		Atlanto-occipital joints, art. atlantooccipitalis
Saddle, art. sellaris	Frontal, sagittal	Flexion, flexio, extension, extension, abduction, abduction, adduction, adductio	Carpometacarpal joint of the thumb, art. Carpometacarpea pollicis
Ellipse, art. ellipsoidea	Frontal, sagittal	Flexion, flexio, extension, extension, abduction, abduction, adduction, adductio	Wrist joint, art. radio-carpea

Triaxial (multi-osseous) joints

Spherical, art. spheroidea		Flexion, flexio, extension, extension, abduction, abduction, adduction, adductio	Shoulder joint, art. humeri
flat, art. plana	Frontal, sagittal, vertical	Flexion, flexio, extension, extension, abduction, abduction, adduction, adductio	Facet joints, art. zygapophysialis
Cup-shaped, art. cotylica	Frontal, sagittal, vertical	Flexion, flexio, extension, extension, abduction, abduction, adduction, adductio	Hip joint, art. coxae