Examples of uniaxial joints. Human joints: types and structural features. According to the degree of mobility, there are three main types of joints: fixed, semi-movable and mobile.

Chest joints

Synovial joints of the skull

Joints of the upper limb

Joints of the lower limb

Joints or synovial joints(articulations synoviales) are presented in the form of discontinuous bone connections. They are among the most common types of articulation in human bones and are necessary for the creation of all necessary conditions high body mobility. A simple joint (articulation simplex) is such if two bones were involved in its formation. A complex joint (articulation composita) is such if it is formed from three or more bones.

Each joint consists of obligatory structural elements and auxiliary entities. Basic elements allow joints to relate specifically to a number of joints. These include articular cartilage and surfaces, joint capsules and cavities. Accessory structures allow joints to have certain functional and structural differences.

Articular cartilage (cartilage articulares) consists of hyaline cartilage, but sometimes it can be constructed of fibrocartilage. It is necessary to cover bones that articulate and face each other. One surface of such a joint is fused with the surface of the bone, and the second part is freely located in the joint.

The articular capsule (capsula articularis) is presented in the form of a closed case and is necessary for the articulation of bones facing each other. It consists of fibrous connective tissue and has two layers - two membranes. The outer membrane also consists of fibrous fabric and is intended to perform a mechanical role. Inside, the first membrane passes into the second - the synovial membrane. Here it forms synovial folds (stratum synoviale), secretes synovium or synovial fluid into the joint, which nourishes the articular cartilage itself, as well as the surfaces of the bones, plays the role of a shock absorber and significantly changes the mobility of the joint. All this is ensured by viscosity synovial fluid(synovia). Moreover, it is precisely due to the synovial folds and villi (vilii synoviales), which face the articular cavity, that the working surface of the membrane increases significantly.

The articular cavity (cavitas articularis) is a narrow closed gap, which is limited by articulating bones and a fluid-filled capsule. This cavity does not have the ability to communicate with the atmosphere.

The auxiliary parts and formations of the joints are quite diverse. These include ligaments, articular discs, menisci and labrums. Each of the above entities should be described in more detail.

Joint ligaments (ligamenta) are presented in the form of bundles of dense connective fibrous tissue. They are necessary to strengthen the joint capsule and limit the guiding movements of bones in the joints. There are capsular, extracapsular ligaments and intracapsular ligaments. The first type of ligaments (capsularia) is located in the thickness of the capsule itself, namely between the fibrous and synovial membrane. Extracapsular ligaments are located on the outside of the composite capsule. They are harmoniously woven into the outer part of the fibrous layer. And the intracapsular ligaments are located precisely inside the joint, but are separated from its cavity synovial membrane. In general, almost all joints in our body have such ligaments.

Articular discs (disci articulares) are layers of fibrous or hyaline cartilage that are wedged between the articular surfaces. They are attached to the joint capsule and divide it into two floors. Thus, the discs increase the conformity of surfaces, volume and variety of movements. Therefore, the articular discs play the role of shock absorbers and significantly reduce shocks and shocks that occur during movement.

Articular menisci (menisci articulares) are presented in the form of crescent-shaped formations of fibrous cartilage. They are necessary to absorb a variety of movements. For example, in every knee joint there are two menisci, which are attached to the capsule located to tibia, as well as the other sharper end, are freely located in the joint cavity.

The labrum (labra articularia) is a dense formation of fibrous connective tissue. It is located at the edge of the glenoid cavity and is necessary to deepen it and increase the conformity of the surfaces. The labrum goes directly into the cavity of the joint itself.

Joints can also vary in shape and degree of mobility. According to their shape, we can distinguish spherical or cup-shaped joints, flat, ellipsoidal and saddle-shaped, ovoid and cylindrical, as well as trochlear and condylar joints.

It is important to note that the nature of possible movements in the joint depends on the shape. For example, spherical and flat knuckles have a generatrix in the form of a segment of a circle, so they allow movement around three axes perpendicular to each other (frontal, sagittal and vertical). That's why shoulder joint, having a spherical shape (articulations spheroideae), allows flexion and extension relative to the frontal axis, as well as combining this action with the sagittal axis or abducting and adducting the action relative to the frontal plane. Also around the frontal axis, rotation can be carried out relative to the horizontal axis with turns inward or outward. In flat joints, movements are quite limited, because the flat surface looks like a small segment of a circle large diameter. Ball-shaped joints allow you to perform actions with a fairly large amplitude of rotation, as well as with the addition of leading actions in a circle. In the latter case, the center of rotation will be the ball-and-socket joint, and the moving bone will describe the so-called cone surface.

Biaxial joints are those joints that can only move around two axes at the same time. These include wrist joints in the form of ellipsoid joints, as well as the carpometacarpal joint of the first finger of the hand in the form of a saddle joint.

Uniaxial joints include cylindrical (articulations trochoideae) and block-shaped (ginglymus) types of joints. In the first case, the movement occurs parallel to the axis of rotation. For example, the atlantoaxial median joint with a vertical axis of rotation, which passes through the second tooth cervical vertebra and proximal radioulnar joint. In the second case, the generatrix of the joint is knee or beveled relative to the axis of rotation. An example of this type of joint is the interphalangeal or ulnohumeral joint.

Condylar joints (articulations bicondylares) are slightly modified elliptical joints (articulations ellipsoideae).

In general, there are cases when movements can only be realized with simultaneous movement of adjacent joints. They are anatomically isolated but united common function. This combination should be taken into account when studying the structure of the human skeleton and when analyzing the structure of movements.

The human skeleton is made up of all kinds of joints. Thanks to them, the bones glide smoothly without interfering with each other.

Bones, muscles, joints and ligaments form a single musculoskeletal system . The joints play one of the key roles in this complex.

Due to them they are fulfilled important functions: maintaining body position, moving individual parts of the body.

Wherever there is a solid bone organ, there is a bone joint. The only place where they are absent is the hyoid bone in the neck.

What are human joints?

articulatio) is a movable connection ( joint) two ends of the bones. The movable joint is responsible for the mobility of rigid skeletal structures.

Some are more mobile, others less, and others remain without movement at all. It all depends on:

How much bonding material is between the ends of the skeletal joint.
What is the composition of the binder material.
What is the shape of the surfaces?
How tense and what position the muscles and ligaments occupy.

Taking these criteria into account, joints are divided into two types.

What types of joints are there and where are they located?

In medical circles they are spoken of as functional and structural.

Functional

Articulatio, components this group, differ in the volume of movements performed:

Synarthrosis (immobile). Location: skeleton of the torso and skull. They protect internal organs from damage.
Amphiarthroses (weakly mobile). They perform similar functions as synarthrosis. Location: skull, skeleton of the body.
Diarthroses (mobile with synovial membrane). Carry out movement in a wide range. Location: upper and lower limbs.

Structural

This group is subdivided:

Fibrous, consisting of fibrous fabric without a slit-like, hermetically sealed space, motionless. Among them:
Nail-shaped, penetrating like a rod into the depths. These include teeth anchored in bone tissue jaws.
Syndesmotic- sedentary fibrous dense formations of connective tissue between the ulna and paired bones in the forearm.
Suture- fixed sutures of the skull.
Synchondrosis- motionless cartilaginous joints at the base of the skull. They are epiphyseal growth plates long bones. Prone to ossification. For example: a joint that unites the most wide part sternum with the first arcuate flat bone.
Synovial- movable. Their slit-like space is filled with synovial fluid, which acts as a lubricant. Articular cartilage covers the top of the bones. The capsule, together with the ligaments, passes into the periosteum. The lateral ligament connects the hand and the bone.

Movable connections with the synovial membrane are divided into:

Flat (sliding): sacroiliac joint. articulation between the acromion and the clavicle. Department upper limbs formed by eight bones. ankles. intervertebrae.
Elliptical (forearm and hand). Atriculatio resembles the shape of an ellipse. Due to it, circular rotations are carried out.
Saddle. The convex shape combined with the concave shape allows for a greater range of motion. The metacarpal joint on the thumb has this shape.
Condylar. The ball-shaped end of the bone is inserted into a depression in another bone. Responsible for flexion, extension, rotation movements. The condylar joints include the metacarpophalangeal joints of the fingers, except the lateral ones.
Ball (shoulder). A convex ball-shaped head inserted into a concave articular cavity. It is considered the freest connection. Performs three-axis movement.
Block-shaped. The surface is cylindrical, located in the frontal plane perpendicular to the sagittal and segmental planes. Example: interphalangeal, ulnar bone joints.
Articulated. A cylindrical surface that protrudes and rotates along a ring formed by ligaments. The elbow is hinged.
Symphyseal. The surfaces are covered with hyaline cartilages fused with fibrous ones. Is sedentary. Example: intervertebral joints, symphysis pubis.
Cartilaginous. They do not have a cavity. The main element is hyaline cartilage or fibrous disc. They are classified as sedentary or immobile.

Each articulatio performs significant function, which promotes the coordinated functioning of the musculoskeletal system.

What elements do joints consist of?

The main components of articulatio: cavity, bony epiphyses, bursa or capsule, cartilage, synovial membrane and fluid.

The fluid fills the gap, performing the function of a lubricant, which promotes the smooth sliding of the articular surfaces.

Hyaline cartilage or fibrous disc forms the articulatio. The articular capsule surrounds the articulating ends of the bones and passes along the articular surface into the periosteum.

Tendons and muscles strengthen the joint capsule, facilitating movement in the desired direction. Menisci in the shape of a crescent moon - additional education, strengthening articulatio.

Skeletal joints are equipped with an arterial and nervous network.

The category of bone connection is determined by the number of articular surfaces:

Simple, for example interphalangeal, has 2 articulating surfaces.
Difficult(elbow) - several simple joints, each performing its own movement separately.
Complex(temporomandibular) - a two-chamber joint with intra-articular cartilage.
Combined(radiulnar) - 2 separate joints, but performing one function.

Anatomy of human joints

Joint name	Articular surface	Articular cartilage	Joint capsule	Form
Sternoclavicular	Surface of the clavicle (sternal), clavicular notch of the sternum	Articular disc		Complex flat
Brachial	Scapula cavity, head humerus	Articular labrum	Attaches to the bony edge of the scapula cavity, runs along the humeral head, ends at the neck	Globular
Humeral-ulnar	Block-shaped notch radius, shoulder block	Articular disc		Screw-shaped
Acromioclavicular	Acromial surface of the clavicle, surface of the acromion	Articular disc		Flat
Brachioradial	Fossa of the head of the radius, head of the condyle of the humerus			Globular
Radiocarpal	Carpal plane of the radius, proximal surfaces of the first row of wrists	Articular disc		Complex, complex, elliptical
Radioulnar proximal	Radial notch ulna, radial circle	Articular disc	Fixed on the neck of the radius, covering 2/3 of the fossa of the elbow in the back, the coronoid, radial in front, does not affect the epicondyles	Cylindrical
Hip	Head femur, semilunar plane of the acetabulum of the pelvic bone	Articular labrum		Cup-shaped spherical
Knee	Articular plane of the kneecap, condyle, surface of the femur, superior surface of the tibia	Meniscus	Attached, retreating from the edges of the planes of the patella, tibia, goes around the patella surface from above, rising upward, passes between the condyles, epicondyles on the sides	Complex, condylar, complex
Ankle	Block of the talus, tibial plane, surfaces of both ankles		Attaches to planes along the cartilaginous edge, grips part of the talus neck anteriorly	Complex block-shaped

As you can see, all bone joints fit harmoniously into general skeleton humans and perform an important musculoskeletal role.

In each joint, basic elements and accessory formations are distinguished.

TO main The elements include the articular surfaces of the connecting bones, the articular capsule surrounding the ends of the bones, and the articular cavity located inside the capsule.

1) Articular surfaces connecting bones are usually covered with hyaline cartilage tissue(cartilago articularis), and, as a rule, correspond to each other. If one bone has a convex surface ( articular head), then on the other it is correspondingly concave (glenoid cavity). Articular cartilage is devoid of blood vessels and perichondrium. It consists of 75-80% water, and 20-25% of the mass is dry matter, about half of which is collagen combined with proteoglycans. The first gives the cartilage strength, the second – elasticity. Articular cartilage protects the articular ends of bones from mechanical stress, reducing pressure and distributing it evenly over the surface.

2 ) Joint capsule (capsula articularis) , surrounding the articular ends of the bones, firmly fuses with the periosteum and forms a closed articular cavity. The capsule consists of two layers: the outer fibrous and the inner synovial. Outer layer It is represented by a thick, durable fibrous membrane formed by fibrous connective tissue, the collagen fibers of which are directed predominantly longitudinally. The inner layer of the joint capsule is formed by a thin, smooth, shiny synovial membrane. The synovial membrane consists of flat and villous parts. The latter has many small outgrowths facing the joint cavity - synovial villi, very rich in blood vessels. The number of villi and folds of the synovial membrane is directly proportional to the degree of joint mobility. The cells of the inner synovial layer secrete a specific, viscous, clear liquid yellowish color - synovium.

3) Synovia (synovia) moisturizes the articular surfaces of bones, reduces friction between them and is a nutrient medium for articular cartilage. In its composition, synovia is close to blood plasma, but contains less protein and has greater viscosity (viscosity in arbitrary units: synovia is 7, and blood plasma is 4.7). It contains 95% water, the rest - proteins (2.5%), carbohydrates (1.5%) and salts (0.8%). Its amount depends on the functional load falling on the joint. Even in such large joints, like the knee and hip, its amount does not exceed an average of 2-4 ml in humans.

4) Articular cavity (cavum articulare) is located inside the articular capsule and is filled with synovium. The shape of the articular cavity depends on the shape of the articulating surfaces, the presence of auxiliary devices and ligaments. A special feature of the joint capsule is that the pressure in it is below atmospheric.

JOINT

Basic elements Additional education

1.Articular surfaces 1.Articular discs and menisci

connecting bones 2. Articular ligaments

2. Articular capsule 3. Articular labrum

3.Articular cavity 4.Synovial bursae and vagina

TO additional joint formations include:

1) Articular disks And menisci (discus et meniscus articularis). They are built from fibrous cartilage and are located in the joint cavity between the connecting bones. For example, there are menisci in the knee joint, and a disc in the temporomandibular joint. They seem to smooth out the unevenness of the articulating surfaces, make them congruent, and absorb shocks and jolts during movement.

2) Articular ligaments (ligamentum articularis). They are built from dense connective tissue and can be located both outside and inside the articular cavity. Articular ligaments strengthen the joint and limit the range of movement.

3) Articular labrum (labium articularis) consists of cartilaginous tissue, is located in the form of a ring around the articular cavity and increases its size. The shoulder and hip joints have a labrum.

4) The auxiliary formations of joints are treated the same bursae (bursa synovialis) and synovial vaginas (vagina synovialis) – small cavities formed by the synovial membrane and filled with synovial fluid.

Axes and types of movement in joints

Movements in the joints occur around three mutually perpendicular axes.

Around frontal axis Maybe:

A) flexion (flexio) , i.e. decreasing the angle between connecting bones;

B) extension (extensio) , i.e. increasing the angle between connecting bones.

Around sagittal axis Maybe:

A) lead (abductio) , i.e. removal of a limb from the body;

B) cast (adductio) , i.e. bringing the limb closer to the body.

Around longitudinal axis rotation possible:

A) pronation (pronatio), i.e. rotation inward;

B) supination (supinatio), i.e. outward rotation;

IN) circling (circumductio)

Phylo-ontogenesis of skeletal bone joints

In cyclostomes and fish leading an aquatic lifestyle, the bones are connected through continuous joints (syndesmosis, synchondrosis, synostosis). Landing led to a change in the nature of movements, in connection with this, transitional forms (symphyses) and the most mobile joints - diarthrosis - were formed. Therefore, in reptiles, birds and mammals, the dominant joint is the joint.

In accordance with this, in ontogenesis, all bone joints go through two stages of development, reminiscent of those in phylogeny, first continuous, then discontinuous (joints). Initially, at the early stage of fetal development, all the bones are connected to each other continuously, and only later (at the 15th week of fetal development in cattle) in the places where future joints are formed, the mesenchyme, which forms the layers between the bones, resolves and a gap filled with synovium is formed. Along the edges of the connecting bones, an articular capsule is formed, which forms the articular cavity. By the time of birth, all types of bone connections are formed and the newborn is able to move. IN at a young age articular cartilage is much thicker than in the old age, since in old age there is a thinning of the articular cartilage, a change in the composition of the synovium, and even - may occur ankylosis joint, i.e. bone fusion and loss of mobility.

Classification of joints

Each joint has a certain shape, size, structure and makes movements around certain planes.

Depending on this, there are several classifications of joints: by structure, by the shape of the articular surfaces, by the nature of movement.

Based on their structure, the following types of joints are distinguished::

1. Simple (art.simplex). The articular surfaces of two bones (humeral and hip-femoral joints) take part in their formation.

2. Complex (art.composita). Three or more articular surfaces of bones (carpal, tarsal joints) take part in their formation.

3. Complex(art. complexa)c contain additional cartilage in the form of a disc or meniscus (knee joint) in the articular cavity.

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

1. Globular joints ( art. spheroidea). They are characterized by the fact that the surface of one of the connecting bones has the shape of a ball, while the surface of the other is somewhat concave. A typical ball and socket joint is the shoulder.

2. Ellipsoidal joints ( art. ellipsoidea). They have articular surfaces (both convex and concave) in the form of an ellipse. An example of such a joint is the occipito-atlas joint.

3. Condylar joints (art. condylaris) have articular surfaces in the form of a condyle (knee joint).

4. Saddle joints (art. sellaris). Characterized by the fact that their articular surfaces resemble part of the surface of the saddle. A typical saddle joint is the temporomandibular joint.

5. Cylindrical joints (art. trochoidea) have articular surfaces in the form of segments of a cylinder, one of them convex, the other concave. An example of such a joint is the atlas-axial joint.

6. Block-shaped joints (ginglimus) are characterized in such a way that the surface of one bone has a depression, and the surface of the other has a protrusion that guides it, corresponding to the depression. An example of block-shaped joints is the finger joints.

7. Flat joints (art.plana) characterized by the fact that the articular surfaces of the bones correspond well to each other. Mobility in them is low (sacroiliac joint).

According to the nature of the movement, they distinguish:

1. Multi-axle joints. In them, movement is possible along many axes (flexion-extension, adduction-abduction, supination-pronation). Examples of these joints include the shoulder and hip joints.

2. Biaxial joints. Movement is possible along two axes, i.e. Possible flexion-extension, adduction-abduction. For example, the temporomandibular joint.

3. Uniaxial joints. The movement occurs around one axis, i.e. Only flexion-extension is possible. For example, elbow, knee joints.

4. Without axles joints. They do not have an axis of rotation and only the sliding of bones relative to each other is possible. An example of these joints would be the sacroiliac joint and the hyoid bone joints, where movement is extremely limited.

5. Combined joints. Includes two or more anatomically isolated joints that function together. For example, the carpal and tarsal joints.

Have you ever thought about what joints are? What role do they play in the human body? With their help, we can make any movements: sit, stand, run, dance, play sports, etc. There are a number of them in the human body great amount and each is responsible for a specific area. To learn more about the structure of the joint, its features and types, we suggest you read our article.

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Anatomical features

Human joints are the basis of every body movement. They are found in all bones of the body (the only exception is the hyoid bone). Their structure resembles a hinge, due to which the bones slide smoothly, preventing their friction and destruction. A joint is a movable connection of several bones, and in the body there are more than 180 of them in all parts of the body. They are immobile, partially movable, and the main part is represented by movable joints.

The degree of mobility depends on the following conditions:

volume of connecting material;
type of material inside the bag;
shapes of bones at the point of contact;
the level of muscle tension, as well as ligaments inside the joint;
their location in the bag.

How is the joint structured? It looks like a bag of two layers that surrounds the junction of several bones. The bursa seals the cavity and promotes the production of synovial fluid. It, in turn, acts as a shock absorber for bone movements. Together they perform three main functions of the joints: they help stabilize the body position, are part of the process of movement in space, and ensure the movement of parts of the body in relation to each other.

Basic elements of a joint

The structure of human joints is complex and is divided into the following basic elements: cavity, capsule, surface, synovial fluid, cartilage, ligaments and muscles. We'll talk briefly about each below.

The joint cavity is a slit-like space, which is hermetically sealed and filled with synovial fluid.
Joint capsule - consists of connective tissue that envelops the connecting ends of the bones. The capsule is formed on the outside from a fibrous membrane, but inside it has a thin synovial membrane (a source of synovial fluid).
Articular surfaces have a special shape, one of them is convex (also called the head), and the second is pit-shaped.

Synovial fluid. Its main function is to lubricate and moisturize surfaces; it also plays an important role in fluid exchange. It is a buffer zone various movements(pushes, jerks, squeezing). Provides both sliding and divergence of bones in the cavity. A reduction in the amount of synovium leads to a number of diseases, bone deformations, and loss of a person’s ability to perform normal functions. physical activity and, as a result, even disability.
Cartilage tissue (thickness 0.2 - 0.5 mm). The surfaces of the bones are covered with cartilage tissue, the main function of which is shock absorption during walking and sports. The anatomy of cartilage is composed of connective tissue fibers that are filled with fluid. This, in turn, nourishes the cartilage when it is at rest, and during movement it releases fluid to lubricate the bones.
Ligaments and muscles are auxiliary parts of the structure, but without them the normal functionality of the entire body is impossible. With the help of ligaments, bones are fixed without interfering with movements of any amplitude due to their elasticity.

The inert protrusions around the joints also play an important role. Their main function is to limit the range of motion. As an example, consider the shoulder. There is a bony tubercle in the humerus. Due to its location next to the process of the scapula, it reduces the range of motion of the arm.

Classification and types

In development human body, way of life, mechanisms of human interaction and external environment, the need to perform various physical actions and various types of joints were obtained. The classification of joints and its basic principles are divided into three groups: the number of surfaces, the shape of the end of the bones, and functionality. We'll talk about them a little later.

The main type in the human body is synovial joint. His main feature- connection of bones in the bag. This type includes shoulder, knee, hip and others. There is also a so-called facet joint. Its main characteristic is the limitation of rotation to 5 degrees and tilt to 12 degrees. The function also consists of limiting the mobility of the spine, which helps maintain the balance of the human body.

By structure

In this group, the classification of joints occurs depending on the number of bones that connect:

A simple joint is a connection between two bones (interphalangeal bones).
Complex – a connection of more than two bones (elbow). The characteristics of such a connection imply the presence of several simple bones, while the functions can be implemented separately from each other.
Complex joint - or two-chamber, which contains cartilage that connects several simple joints ( lower jaw, radioulnar). Cartilage can separate the joints either completely (disc shape) or partially (meniscus in the knee).
Combined - combines isolated joints that are placed independently of each other.

According to the shape of the surfaces

The shapes of the joints and the ends of the bones have the shape of various geometric shapes (cylinder, ellipse, ball). Depending on this, movements are carried out around one, two, or three axes. There is also a direct relationship between the type of rotation and the shape of the surfaces. Further, detailed classification joints according to the shape of its surfaces:

Cylindrical joint - the surface has the shape of a cylinder, rotates around one vertical axis (parallel to the axis of the connected bones and the vertical axis of the body). This species may have a rotational name.
Block joint - a cylinder-shaped joint (transverse), one axis of rotation, but in the frontal plane, perpendicular to the connected bones. Characteristic movements are flexion and extension.
Helical is a variation of the previous type, but the axes of rotation of this form are located at an angle other than 90 degrees, forming helical rotations.
Ellipsoidal - the ends of the bones have the shape of an ellipse, one of them is oval, convex, the second is concave. Movements occur in the direction of two axes: bend-unbend, abduct-addite. The ligaments are perpendicular to the axes of rotation.
Condylar is a type of ellipsoidal. The main characteristic is the condyle (a rounded process on one of the bones), the second bone is in the shape of a depression, and can differ significantly in size from each other. The main axis of rotation is represented by the frontal one. The main difference from the block-shaped one is the strong difference in the size of the surfaces, from the ellipsoidal one - the number of heads of connecting bones. This type has two condyles, which can be located either in the same capsule (similar to a cylinder, similar in function to the trochlear one) or in different capsules (similar to the ellipsoidal one).

Saddle-shaped - formed by connecting two surfaces as if “sitting” on each other. One bone moves lengthwise, while the second moves across. Anatomy involves rotation around perpendicular axes: flexion-extension and abduction-adduction.
Ball-and-socket joint - the surfaces are shaped like balls (one convex, the other concave), due to which people can make circular movements. Basically, rotation occurs along three perpendicular axes, the intersection point being the center of the head. The peculiarity is a very small number of ligaments, which does not interfere with circular rotations.
Cup-shaped - the anatomical appearance involves a deep depression of one bone that covers most head area of the second surface. As a result, there is less free mobility compared to the spherical one. Necessary for greater joint stability.
Flat joint - flat ends of bones of approximately the same size, interaction along three axes, the main characteristic is a small range of motion and surrounded by ligaments.
Tight (amphiarthrosis) - consists of bones of different sizes and shapes that are closely connected to each other. Anatomy: inactive, surfaces are represented by tight capsules, non-elastic short ligaments.

By nature of movement

In view of their physiological characteristics joints perform many movements along their axes. In total, there are three types in this group:

Uniaxial - which rotate around one axis.
Biaxial - rotation around two axes.
Multi-axis - mainly around three axes.

Axis classification	Kinds	Examples
Uniaxial	Cylindrical	Atlanto-axial median
	Block-shaped	Interphalangeal joints of the fingers
	Helical	Humeral-ulnar
Biaxial	Ellipsoidal	Radiocarpal
	Condylar	Knee
	Saddle	Carpometacarpal joint of the thumb
Multi-axis	Globular	Brachial
	Cup-shaped	Hip
	Flat	Intervertebral discs
	Tight	Sacroiliac

In addition, there are also different types joint movements:

Flexion and extension.
Rotation in and out.
Abduction and adduction.
Circular movements (surfaces move between axes, the end of the bone draws a circle, and the entire surface draws the shape of a cone).
Sliding movements.
Removing one from another (example, peripheral joints, distance of fingers).

The degree of mobility depends on the difference in the size of the surfaces: the larger the area of one bone over another, the greater the range of movement. Ligaments and muscles can also inhibit range of motion. Their presence in each type is determined by the need to increase or decrease the range of motion of a certain part of the body.

Anatomy Tour Video

In the next video you can visually study the anatomy and see how the joints on the skeleton work.

With the presence of a gap between the articulating bones. A joint is a type of bone articulation; another type of joint - continuous connection bones (without 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, 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 liquid yellowish color. 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. Outflow there's blood coming out along the veins into adjacent 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 depression.

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

The shape of the articular surfaces of the bones is compared to geometric shapes 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-axis (spherical ) 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.