Human bone is so hard that it can support about 10 thousand kilograms, but if the skeleton consisted of only one hard bone, our movement would be impossible. Nature solved this problem simply by dividing the skeleton into many bones and creating joints, the places where the bones intersect.
Human joints perform a rather important function. Thanks to them, the bones, teeth and cartilage of the body are attached to each other.
Types of human joints
They can be classified by functionality:
A joint that does not allow movement is known as synarthrosis. Skull sutures and gomphos (connection of teeth to the skull) are examples of synarthroses. Connections between bones are called syndesmoses, between cartilage - synchordroses, bone tissue - synthostoses. Synarthroses are formed with the help of connective tissue.
Amphiarthrosis allows little movement of the connected bones. Examples of amphiarthrosis are the intervertebral discs and the pubic symphysis.
The third functional class is free-moving diarthrosis. They have the mosthigh range of motion. Examples: elbows, knees, shoulders and wrists. These are almost always synovial joints.
The joints of the human skeleton can also be classified according to their structure (the material they are made of):
Fibrous joints are made up of tough collagen fibers. These include the sutures of the skull and the joint that joins the ulna and radius of the forearm together.
Cartilaginous joints in humans are made up of a group of cartilage that connect bones together. Examples of such connections would be the joints between the ribs and costal cartilage, and between the intervertebral discs.
The most common type, the synovial joint, is a fluid-filled space between the ends of the bones being bonded. It is surrounded by a capsule of rigid dense connective tissue covered with a synovial membrane. The synovial membrane that makes up the capsule produces an oily synovial fluid whose function is to lubricate the joint, reducing friction and wear.
There are several classes of synovial joints, such as ellipsoid, trochlear, saddle and ball joints.
Ellipsoid joints connect smooth bones together and allow them to slide past each other in any direction.
Oblocate joints, such as the human elbow and knee, restrict movement in only one direction so that the angle between the bones can be increased or decreased. Limited movement in the trochlear joints provides more strength and strength to the bones, muscles and ligaments.
Saddle joints such asbetween the first metacarpal bone and the trapezoid bone, allow the bones to rotate 360 degrees.
The human shoulder and hip joints are the only ball-and-socket joints in the body. They have the freest range of motion, they are the only ones that can turn on their axis. However, the disadvantage of ball joints is that the free range of motion makes them more susceptible to dislocation than less mobile human joints. Fractures are more common in these places.
Some synovial types of human joints need to be considered separately.
Block joint
Block joints are a class of synovial joints. These are the ankles, knee and elbow joints of a person. Usually a trochlear joint is a ligament of two or more bones where they can only move in one axis to flex or straighten.
The simplest trochlear joints in the body are the interphalangeal joints, located between the phalanges of the fingers and toes.
Because they have little body mass and mechanical strength, they are composed of simple synovial material with tiny extra ligaments to strengthen them. Each bone is covered with a thin layer of smooth hyaline cartilage, designed to reduce friction in the joints. The bones are also surrounded by a capsule of tough fibrous connective tissue covered by a synovial membrane.
The structure of a human joint is always different. For example, the elbow joint is more complex, being formed between the humerus, radius and ulna of the forearm. The elbow is subjected to more stress thanjoints of the fingers and toes, therefore contains several strong additional ligaments and unique bone structures that strengthen its structure.
The ulna and radius collateral ligaments help support the ulna and radius and strengthen the joints. Human legs also consist of several large block-like joints.
The ulna-like ankle joint is located between the tibia and fibula in the lower leg and the talus in the leg. Branches of the tibia fibula form a bony socket around the talus to limit movement of the leg in one axis. Four additional ligaments, including the deltoid, hold the bones together and strengthen the joint to support the weight of the body.
Located between the femur and the tibia and fibula of the lower leg, the knee joint is the largest and most complex trochlear joint in the human body.
The elbow joint and ankle joint, which have similar anatomy, are the most commonly affected by osteoarthritis.
Ellipsoid joint
An ellipsoid joint, also known as a flat joint, is the most common form of synovial joint. They are formed near bones that have a smooth or almost smooth surface. These joints allow the bones to slide in any direction - up and down, left and right, diagonally.
Due to their structure, ellipsoid joints are flexible, while their movement is limited (to prevent injury). Ellipsoid joints are covered with synovial membrane, whichproduces a fluid that lubricates the joint.
Most ellipsoid joints are found in the appendicular skeleton between the carpal bones of the wrist, between the carpal joints and metacarpal bones of the hand, between the bones of the ankle.
Another group of ellipsoid joints is located between the faces of twenty-six vertebrae in the intervertebral joints. These connections allow us to flex, extend, and rotate the torso while maintaining the strength of the spine, which supports the weight of the body and protects the spinal cord.
Condylar joints
There is a separate type of ellipsoid joints - the condylar joint. It can be considered a transitional form from a block-shaped joint to an ellipsoid one. The condylar joint differs from the block joint in a large difference in the shape and size of the articulating surfaces, as a result of which movement around two axes is possible. The condylar joint differs from the ellipsoid joint only in the number of articular heads.
Saddle joint
The saddle joint is a type of synovial joint where one of the bones is shaped like a saddle and the other bone rests on it like a rider on a horse.
Saddle joints are more flexible than ball joints or ellipsoids.
The best example of a saddle joint in the body is the carpometacarpal joint of the thumb, which is formed between the trapezoid bone and the first metacarpal bone. In this example, the trapezium forms a rounded saddle on which the first metacarpal sits. carpometacarpal jointallows the person's thumb to easily cooperate with the other four fingers of the hand. The thumb is of course extremely important to us, as it is what allows our hand to grip objects firmly and use many tools.
Ball Joint
Ball joints are a special class of synovial joints that have the highest freedom of movement in the body due to their unique structure. The human hip and shoulder joint are the only ball joints in the human body.
Two main components of the ball joint: a bone with a spherical head and a bone with a cup-shaped notch. Consider the shoulder joint. Human anatomy is so arranged that the spherical head of the humerus (upper arm bone) fits into the glenoid cavity of the scapula. The glenoid cavity is a small and shallow depression that gives the shoulder joint the greatest range of motion in the human body. It is surrounded by a ring of hyaline cartilage, which is the flexible reinforcement of the bone, while the muscles - the cuffs of the rotator - keep the humerus within the socket.
The hip joint is somewhat less mobile than the shoulder, but is a stronger and more stable joint. Extra stability of the hip joint is needed to support the weight of a person's body on their feet while performing activities such as walking, running, etc.
At the hip joint, the rounded, almost spherical head of the femur (femur) fits snugly againstacetabulum, a deep recess in the pelvic bone. A sufficiently large number of stiff ligaments and strong muscles hold the head of the femur in place and resist the most severe stresses in the body. The acetabulum also prevents hip dislocations by limiting movement of the bone within it.
Based on all of the above, you can make a small table. The structure of the human joint will not be included in it. So, in the first column of the table, the type of joint is indicated, in the second and third - examples and their location, respectively.
Human joints: table
Joint type |
Examples of joints |
Where are you |
| Blocky | Knee, elbow, ankle joint. The anatomy of some of them is shown below. | Knee - between the femur, tibia and patella; ulna - between the humerus, ulna and radius; ankle - between the lower leg and foot. |
| Ellipsoid | Intervertebral joints; joints between the phalanges of the fingers. | Between the faces of the vertebrae; between the phalanges of the toes and hands. |
| Globular | Hip and shoulder joint. Human anatomy pays special attention to this type of joints. | Between the femur and pelvic bone; between the humerus and the shoulder blade. |
| Saddle | Carpometacarpal. | Between the trapezoid bone and the first metacarpal bone. |
To make it clearer what the human joints are, let's describe some of them in more detail.
Elbow joint
Human elbow joints, the anatomy of which has already been mentioned, require special attention.
The elbow joint is one of the most complex joints in the human body. It is formed between the distal end of the humerus (more precisely, its articular surfaces - the block and condyle), the radial and block-shaped notches of the ulna, as well as the head of the radius and its articular circumference. It consists of three joints at once: humeroradial, humeroulnar and proximal radioulnar.
The glenohumeral joint is located between the trochlear notch of the ulna and the block (articular surface) of the humerus. This joint belongs to the block-shaped and is uniaxial.
The shoulder joint is formed between the condyle of the humerus and the head of the humerus. Movements in the joint are made around two axes.
The promaximal radioulnar connects the radial notch of the ulna and the articular circumference of the head of the radius. It is also single axle.
There are no lateral movements in the elbow joint. In general, it is considered a trochlear joint with a helical sliding shape.
The largest of the upper body are the elbow joints. Human legs are also made up of joints that simply cannot be ignored.
Hip joint
This joint is located between the acetabulum on the pelvic bone and the femur (its head).
This head is covered with hyaline cartilage almost throughout, except for the fossa. The acetabulum is also covered with cartilage, but only near the lunate surface, the rest of it is covered with synovial membrane.
The hip joint includes the following ligaments: ischiofemoral, iliofemoral, pubic-femoral, circular zone, as well as the ligament of the femoral head.
The iliofemoral ligament originates at the inferior anterior iliac bone and ends at the intertrochanteric line. This ligament is involved in maintaining the trunk in an upright position.
The next ligament, the ischiofemoral ligament, starts at the ischium and is woven into the capsule of the hip joint itself.
Slightly higher, at the top of the pubic bone, begins the pubofemoral ligament, which goes down to the capsule of the hip joint.
Inside the joint itself is the ligament of the femoral head. It starts at the transverse ligament of the acetabulum and ends at the fossa of the femoral head.
The circular zone is designed as a loop: it is attached to the lower anterior iliac bone and surrounds the neck of the femur.
The hip and shoulder joints are the only ball joints in the human body.
Knee joint
This joint is formed by three bones: the patella, the distal end of the femur and the proximal end of the tibiabones.
The knee joint capsule is attached to the edges of the tibia, femur and patella. It is attached to the femur under the epicondyles. On the tibia, it is fixed along the edge of the articular surface, and the capsule is attached to the patella in such a way that its entire front surface is outside the joint.
The ligaments of this joint can be divided into two groups: extracapsular and intracapsular. There are also two lateral ligaments in the joint - the tibial and peroneal collateral ligaments.
Ankle joint
It is formed by the articular surface of the talus and the articular surfaces of the distal ends of the fibula and tibia.
The articular capsule is attached almost throughout its entire length to the edge of the articular cartilage and recedes from it only on the anterior surface of the talus. On the lateral surfaces of the joint are its ligaments.
The deltoid or medial ligament consists of several parts:
- posterior tibio-talar, located between the posterior edge of the medial malleolus and the posterior medial parts of the talus;
- anterior tibio-talar, located between the anterior edge of the medial malleolus and the posteromedial surface of the talus;
- tibiocalcaneal part, extending from the medial malleolus to the support of the talus;
- tibia-navicular part, originates from the medial malleolus and ends at the dorsum of the navicular bone.
The next ligament, the calcaneofibular, extends from the outer surfacelateral malleolus to the lateral surface of the neck of the talus.
Not far from the previous one is the anterior talofibular ligament - between the anterior edge of the lateral malleolus and the lateral surface of the neck of the talus.
And last, the posterior talofibular ligament originates at the posterior edge of the lateral malleolus and ends at the lateral tubercle of the process of the talus.
In general, the ankle joint is an example of a trochlear joint with helical motion.
So, now we definitely have an idea of what human joints are. The anatomy of the joints is more complicated than it seems, and you can see for yourself.
