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 bone articulation; another type of articulation - a continuous connection of bones (without a joint space) - is called synarthrosis. Joints perform both supporting and motor functions.

Rice. 1. 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 - ellipsoidal;
2 - saddle-shaped;
3 - spherical;
4 - block-shaped.

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

The ends of the articulating bones (epiphyses) form the solid base 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, ensures a more complete fit of the ends of the bones during movement and acts as a shock absorber in the supporting joints.

The articular capsule closes the joint cavity, attaching to the edges of the articular surfaces of the connecting bones. The thickness of this capsule varies. In some joints it is tight, in others it is loose. There are two layers in the capsule: the inner synovial and the 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. The joints are further strengthened by the passing muscles and their tendons.

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

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

The blood supply to the joints occurs due to the branches of the nearest arteries; they form a dense network of anastomoses in the articular capsule. The outflow of blood goes through the veins into nearby venous trunks. Lymphatic drainage occurs through a network of small lymphatic vessels into 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 like 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 completely correspond to each other; often the head has greater curvature and vastness than the cavity.

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

According to their shape, the articular surfaces of the bones are compared with geometric figures and, accordingly, joints are distinguished: spherical, ellipsoidal, block-shaped, saddle-shaped, cylindrical, etc. Movements can be carried out around one, two and three axes, forming one- (cylindrical and block-shaped), two- (ellipsoidal and saddle-shaped) and multi-axial (ball-and-socket) joints (Fig. 2). The number and position of axes determine the nature of the movements. There are movements around the frontal axis - flexion and extension, the sagittal axis - adduction and abduction, the longitudinal axis - rotation and multi-axis 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 distinguished:
1. Simple joint (art. simplex) having only 2 articular surfaces, for example interphalangeal joints.
2. Complex joint (art. composite) having more than two articulating 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 that divides the joint into two chambers (bicameral 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 distinguishes it from compound and complex joints, each of which, being anatomically unified, is composed of functionally different joints.

Classification by form and function 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. 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 to this spherical shape and the heads make it possible to rotate around multiple axes that coincide with the radii of the ball (ball-and-socket joint).
Therefore, between the number of axes and shape articular surfaces there is 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 - trochlear talocrural joint (articulario talocruralis ginglymus)
1b - trochlear interphalangeal joint of the hand (articulatio interpalangea manus ginglymus);
1c - cylindrical humeral-radial joint of the elbow joint, articulatio radioulnaris proximalis trochoidea.

Biaxial joints: 2a - ellipsoidal wrist joint, articulatio radiocarpea ellipsoidea;
2b - condylar knee joint (articulatio genus - articulatio condylaris);
2c - saddle-shaped 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. 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 articulating surfaces eliminate the possibility of lateral slippage and promote movement around a single 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 trochlear joint is considered to be a screw-shaped joint (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 location 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.

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 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 ellipsoidal 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 type of elliptical, representing a transitional shape from the trochlear joint to the ellipsoidal one. Therefore, its main axis of rotation will be the frontal one.

From trochlear 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 trochlear joint, movements around two axes are possible in the condylar joint.

From ellipsoidal joint it differs 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.

Since in the condylar joint of the head do not have the correct elliptical 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 condyles located in different articular capsules, then such a condylar joint is close in function to the ellipsoidal one (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 articulations 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).

III. 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, the 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 flexion occurs, flexio, when the moving part forms an angle with the frontal plane, 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.

Ball and socket joint- 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.

Variety ball and socket joint- cup-shaped 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.

A - uniaxial joints: 1,2 - trochlear 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- cup-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, 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 located on all sides of the joint.

Stiff joints - amphiarthrosis

Under this name there is a group of joints with different shape of articular surfaces, but similar in other characteristics: they have a short, tightly stretched joint 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. friend, 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 knuckles, art. plana, in which, as noted, the flat articular surfaces are equal in area. In tight joints, movements are sliding and 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 - trochlear joint

Video lesson: Classification of joints. Range of motion in 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 classified as the passive part of the musculoskeletal system.

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 collapsing, which is a very painful and dangerous process. In the human body, joints play a triple role: they help maintain body position, 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 coupling of others. In addition, there are non-bone tissues that protect the joint and soften interosseous friction. The structure of the joint is very interesting.

Main elements of the joint:

Joint cavity;

Epiphyses of bones forming a joint. The epiphysis is a rounded, often widened, end section of a tubular bone that forms a joint with the adjacent bone through the articulation of 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 softens their friction.

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

The joint capsule is a sleeve-like fibrous layer that envelops the joint. It gives bones stability and prevents them from moving excessively.

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

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

A joint is an amazing natural mechanism for the movable connection of bones, where the ends of the bones are connected in the articular capsule. Bag the outside is made up of fairly strong fibrous tissue - this is a dense protective capsule with ligaments that help control and hold the joint, preventing displacement. The inside of the articular capsule is synovial membrane.

This membrane produces synovial fluid - the lubricant of the joint, a viscoelastic consistency, which even in a healthy person does not have much of, but it occupies the entire cavity of the joint and is capable of performing important functions:

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

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

3. Acts as a shock absorber and shock absorber.

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

Synovial fluid a healthy joint has all 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 fully perform their functions and allows you to lead an active life.

If the joint is inflamed or painful, then the synovial membrane of the joint capsule produces more synovial fluid, which also contains inflammatory agents that increase swelling, edema, 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. Cartilage, as mentioned, receives nutrition from the synovial fluid and from the bone structure located under the cartilage itself - the subchondral bone.

Cartilage Basically acts as a shock absorber - it reduces the pressure on the mating surfaces of the bones and ensures smooth sliding of the bones relative to each other.

Functions of cartilage tissue

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 arranged connective tissue fibers - the main substance of cartilage, which are formed by special compounds - glycosaminoglycans.
It is the glycosaminoglycans, connected by protein bonds, that form larger structures of cartilage - proteoglycans - that are the best natural shock absorbers, since they have the ability to restore their original shape after mechanical compression.

Due to its special structure, cartilage resembles a sponge - absorbing fluid in a calm state, it releases it into the articular cavity under load and thereby additionally “lubricates” the joint.

Such a common disease as arthrosis upsets the balance between the formation of new and the destruction of 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 irregular, and begins to grow away from the cartilage. This limits movement and causes joint deformation. The joint capsule thickens and becomes inflamed. Inflammatory fluid fills the joint and begins to stretch the capsule and articular ligaments. This creates a painful feeling of stiffness. Visually, you can observe an increase in the volume of the joint. Pain, and subsequently deformation of the joint surfaces with arthrosis, leads to stiff 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.

According to their shape, the articular surfaces of the bones are compared with geometric figures and, accordingly, joints are distinguished: spherical, ellipsoidal, trochlear, saddle-shaped, cylindrical, etc.

Joints with movement

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

. Elbow joint: the connection of the humerus, ulna and radius bones, allowing rotation of the elbow.

. Knee joint: a complex articulation that provides flexion and extension of the leg and rotational movements. At the knee joint, the femur and tibia articulate - the two longest and strongest bones, on which, together with the patella, located in one of the tendons of the quadriceps muscle, almost the entire weight of the skeleton presses.

. Hip joint: connection of the femur with the pelvic bones.

. 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 ensures the movement of the lower leg and foot, but also maintains the concavity of the foot.

The following main types of joint movements are distinguished:

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

The human hand contains: 27 bones, 29 joints, 123 ligaments, 48 nerves and 30 named arteries. We move our fingers millions of times throughout our lives. 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 articular cavity of the scapula.

The articular surface of the scapula is surrounded by a ring of fibrocartilage - the so-called articular lip. The tendon of the long head of the biceps brachii muscle passes through the joint cavity. The shoulder joint is strengthened by the powerful coracohumeral ligament and surrounding muscles - deltoid, subscapularis, supra- and infraspinatus, teres major and minor. The pectoralis major and latissimus dorsi muscles also take part in shoulder movements.

The synovial membrane of the thin joint capsule forms 2 extra-articular inversions - the tendons of the biceps brachii and subscapularis. The blood supply to this joint includes the anterior and posterior arteries, which bend around the humerus, and the thoracoacromial artery; venous outflow is carried out into the axillary vein. The outflow of lymph occurs in the lymph nodes of the axillary region. The shoulder joint is innervated by branches of the axillary nerve.

The shoulder joint is capable of movement around 3 axes. Flexion is limited by the acromion 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 upper limb belt (when the sternoclavicular joint is included) - up to 180°. Abduction stops when the greater tuberosity of the humerus hits the coracoacromial ligament. The spherical shape of the articular surface allows a person to raise his arm, move it back, and rotate the shoulder along with the forearm and 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 formation.

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 intraarticular ligament of the femoral head, as well as the transverse ligament acetabulum, which surrounds the neck of the femur. From the outside, the powerful iliofemoral, pubofemoral and ischiofemoral ligaments are woven into the capsule.

The blood supply to this joint is through the circumflex femoral arteries, branches of the obturator and (variably) 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. Lymphatic drainage occurs in 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 movements 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 experiences a lot of stress, so it is not surprising that its lesions occupy first place in the general pathology of the articular apparatus.

Knee joint

One of the largest and most complex human joints. It is formed by 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 fibular and tibial collateral ligaments, the oblique and arcuate popliteal ligaments, the patellar ligament, and the medial and lateral suspensory ligaments of the patella. The intra-articular ligaments include the anterior and posterior cruciate ligaments.

The joint has many auxiliary elements, such as menisci, intra-articular ligaments, synovial folds, and bursae. Each knee joint has 2 menisci - the outer and the inner. The menisci look like crescents and play 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 bursae, some of which communicate with the joint cavity.

Everyone had to admire the performances of artistic gymnasts and circus performers. People who are able to climb into small boxes and bend unnaturally are said to have gutta-percha joints. Of course, this is not true. The authors of The Oxford Handbook of Body Organs assure readers that “their joints are phenomenally flexible”—medically known as 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 carried forward by raising the hip.

According to the World Health Organization, every 7th person on the planet suffers from joint pain. Between the ages of 40 and 70 years, joint diseases are observed in 50% of people and in 90% of people over 70 years of age.
Based on materials from www.rusmedserver.ru, meddoc.com.ua

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

In each joint, there are articular surfaces of the articulating bones, an articular capsule that surrounds the articular ends of the bones in the form of a coupling, and an articular cavity located inside the capsule between the bones.

Articular surfaces, facies articulares, covered with articular cartilage, cartilago articularis, hyaline, less often fibrous, 0.2-0.5 mm thick. Due to constant friction, articular cartilage becomes smooth, facilitating the sliding of articular surfaces, and due to the elasticity of the cartilage, it softens shocks and serves as a buffer. The articular surfaces are usually more or less consistent with 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 (the glenoid cavity).

Articular capsule, capsula articularis, hermetically surrounding the articular cavity, grows 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 sticky transparent synovial fluid into the joint cavity - synovia, the presence of which reduces friction of the articular surfaces. The synovial membrane ends at the edges of the articular cartilages. 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 thin places of the capsule, bag-like protrusions or inversions of the synovial membrane are formed - synovial bursae, bursae synovidles, located around the tendons or under the muscles lying near the joint. Being made of synovium, these bursae reduce friction of tendons and muscles during movement.

Articular cavity, сavitas articularis, represents a hermetically closed slit-like space, limited by articular surfaces and 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, the synovium plays a role in fluid exchange and in strengthening the joint due to the adhesion of surfaces. It also serves as a buffer, softening the compression and shock of the articular surfaces, since movement in the joints is not only sliding, but also divergence of the articular surfaces. There is negative pressure (less than atmospheric pressure) between the articular surfaces. Therefore, their divergence is prevented by atmospheric pressure. (This explains the sensitivity of the joints to fluctuations in atmospheric pressure in some diseases, which is why such patients can predict worsening weather.)

When the joint capsule is damaged, air enters the joint cavity, causing the articular surfaces to immediately separate. Under normal conditions, the divergence of the articular surfaces, in addition to the 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 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 cartilage tissue and look like either solid cartilaginous plates - discs, disci articulares, or non-solid, crescent-shaped formations and therefore called menisci, menisci articulares (meniscus, Latin - crescent), or in the form of cartilaginous rims, labra articularia (articular lips). All these intra-articular cartilages along their circumference grow together with the articular capsule. They arise as a result of new functional requirements as a reaction 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 promoting joint movement.

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

they help maintain body position;
participate in the movement of body parts in relation to each other and
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:

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.

Sliding movements of the articular surfaces are also possible, as well as moving them away 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 amount 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 also be limited by various types of brakes, the role of which is played by certain ligaments, muscles, bone protrusions, etc. Since increased physical (strength) load 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 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. The amount of movement is also influenced by intra-articular cartilage, which increases the variety of movements. Thus, in the temporomandibular joint, which in terms of the shape of the articular surfaces is classified as a biaxial joint, due to the presence of an intra-articular disc, three types of movements are possible.

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

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

Based on the number of articular surfaces, they are distinguished:

Simple joint (art. simplex) having only 2 articular surfaces, for example interphalangeal joints.
Complex joint (art. composite) having more than two articulating 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.
Complex joint (art. complexa), containing intra-articular cartilage that divides the joint into two chambers (bicameral 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).
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.

By form and by function 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).

We can outline the following unified anatomical and physiological classification of joints.

Uniaxial joints.

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.

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 articulating 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 a screw-shaped joint (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.

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 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.

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. Since the heads in the condylar joint do not have a regular elliptical configuration, the second axis will not necessarily be horizontal, as is typical for 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 one (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.

Saddle joint, art. selldris(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).

Multiaxial joints.

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, the 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:

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 posteriorly;
anteroposterior (sagittal), around which abduction, abductio, and adduction, adductio, occur;
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.

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 ways: 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.

GENERAL INFORMATION

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

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

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

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

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

Based on the shape of the connecting bone edges, the following sutures are distinguished:

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

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

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

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

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

2.Cartilaginous connections, synchondrosis, synchondrosis, are continuous connections of bones through cartilage tissue. Synchondrosis can be temporary or permanent.

Temporary synchondroses include epiphyseal cartilages connecting the diaphyses and epiphyses of tubular bones; cartilage between the sacral vertebrae. Temporary synchondroses persist in childhood and are then replaced by a bone connection - synostosis.

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

3. Bone joints, synostoses, synostosis, are 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 motionless continuous connections, make possible various movements of parts of the human body.

A joint, articulatio, is an organ in which basic and auxiliary elements are distinguished.

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, cartilago articularis, covers the articular surfaces. Most articular surfaces are covered with hyaline cartilage, and only some joints, such as the temporomandibular and sternoclavicular joints, have fibrocartilage.

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

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

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

Synovia is a viscous fluid that is located 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. Articular discs and menisci increase the contact area of the articular surfaces and act as shock absorbers and also play a role in movement.

The labrum, labrum articulare, is a cartilaginous rim attached to 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 can also guide movement.

There are: a) extracapsular ligaments, separated from the articular 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.

Classification of joints

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 the interphalangeal joints.

A complex 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.

Based on the shape of the articular surfaces, joints are classified as spherical, cup-shaped, flat, ellipsoidal, saddle-shaped, condylar, trochlear, and rotational (cylindrical).

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

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

Classification of joints by form and function

Single-spinous joints

Double joints

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

Triaxial (multi-axial) joints

Globular, 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