The knee joint is anatomy. Anatomy of the lower limbs of a person, a picture

In the human body there are 206 bones, most of which do not exceed a few cubic centimeters in size. The most painful and massive bone in the body is the femoral bone. Its structure allows us to walk straight and not to fall. Through the knee joint, the femur connects with the tibial and fibular, forming a free lower limb.

Anatomy of the free lower limb

Anatomy of the lower limbs of a man includes bones, muscles, ligaments, joints and fascia. This if you understand seriously and thoroughly. But for this article will be quite a short excursion into the structure of the foot. So, the lower limb of a person is divided into the thigh, the shin and the foot.

The basis of the thigh is the femur. It is layered overlapping muscles, thanks to which a person can walk, stand, run, swim and much more. Working on the principle of a lever, they act on the hip or knee joint. The anatomy of myofibrils allows them to stretch and contract, adjusting to the needs of the body.

The central part of the lower leg is tibial and fibular bones. Between each other they are connected by a joint and connective tissue membrane, in which the vessels pass. On top of this design, cover several layers of muscles that continue on the foot.

Ankle and foot are parts of the body that experience a constant load. A relatively small area of the sole holds the weight of the whole body (and sometimes it can reach up to three hundred kilograms). The foot consists of the heel bone, tarsus and metatarsus, which are covered with fasciae and muscles. Also this area is abundantly blood supply, so that the muscles always have a supply of oxygen.

Basic structures of the knee joint

What, then, is the anatomy of the human knee ? For a medical university student in the first year, this is one of the most difficult questions, because you need to remember all the structures that form this joint:
- bones (as a basis);
- muscles (contracting, they change the position of the shin);
- nerves and blood vessels (nourish tissues and transmit information from the brain to the periphery);
- Menisci (form the surface of the joint);
- ligaments (keep the bones together);

All of the above components in a healthy person work together, as a single mechanism. But it is worth "breaking" at least one component, and a smooth gait will not work.

Bones

The large bones of the knee joint are the femoral and tibial. But apart from them there is also a small rounded bone, located separately from the others. It is called the patella or knee cap. On the diaphysis of the femur are spherical elevations - condyles covered with cartilage for better slip. They are the upper part of the knee joint. The lower part is formed by a flat head of the tibia, which is also covered with cartilaginous tissue.

The fibula is not long enough to form the knee joint. The anatomy of its head allows it to fit to the tibia in such a way that the shin can be slightly turned without getting fractures. The thickness of the cartilage covering the articular surfaces reaches five millimeters. It is necessary to reduce frictional force, as well as depreciation.

Cross-shaped ligaments

As already mentioned above, in addition to bones and muscles, there are also ligaments of the knee joint. Their anatomy is very entertaining, since it is these strips of tissue that hold all parts of the mechanism together. To strengthen the joint capsule, on the sides of the bones are the medial and lateral collateral (envelopes) ligaments. Between the upper and lower articular surfaces are located cruciform ligaments. Topographically, it is possible to distinguish the anterior and posterior ligaments, which limit the excessive bending and extension of the knee.

Bundles are important elements of the joint. They stabilize it, make the gait harder and avoid dislocations.

Menisci and their function

If you look at the picture of the knee joint, then in addition to the bones, you will see two small formations. These are dense connective tissue formations - menisci. They are located between the femoral and tibia.

The two main functions of the meniscus:
- increase in the area of the joint surface for better distribution of the person's weight;
- Improvement of knee joint stability along with ligaments.

In order to imagine what role a meniscus performs, you need to imagine a ball located on a smooth flat surface. If there is nothing between the ball and the "plateau", it will roll away. Nature does not tolerate emptiness, and therefore inside the joint, too, should not be empty. The connective tissue fills the space between the articular surfaces, increasing their area and guarding against excessive loads. Damage to meniscus is fraught with joint inflammation and destruction of cartilage

Muscles

From the front of the thigh to the knee joint descends the extensor muscles. One end is fixed to the femur or pelvis, and the other end passes into the tendon and is weaved into the joint capsule. The main thing in this group of muscles is the quadriceps. When it contracts, the leg unbends in the joint.

The flexor muscles are located on the posterior surface of the thigh. They also begin on the lower extremity belt, and end in the capsule of the joint in the form of tendons. When this group is cut, the leg is bent.

Nerves and vessels

Nerve fibers, arteries and veins as a network braid the knee joint. The anatomy of the vessels in this area is not fundamentally different from the rest of the body. The artery, accompanied by two veins passes through the back surface of the joint, blood supplying the shin and foot.

Next to them is the popliteal nerve, which is a continuation of the sciatic nerve. A little above the knee joint, it is divided into two parts and already in this form descends on the shin and foot. Thanks to him, a free lower limb produces sensory and motor innervation.

Functional tests of the knee joint

When a knee injury occurs , the trauma specialist needs to find out with physical and hardware methods what is damaged and how serious it all is. It's not enough just to look at the knee joint.

1. Lahman test or drawer symptom. It is performed to determine the damage to the anterior cruciate ligament, if the image of the knee joint could not be made. For this, the patient is placed on his back and the injured leg is bent at the knee joint by thirty degrees. Then the doctor fixes the thigh and simultaneously propels the tibia forward. If the movement is possible, then the bunch is damaged.

2. Contactless test. If, for some reason, the doctor can not touch the patient (for example, there is an obstruction in the form of a blockage or water between them), and a survey is needed, then this technique allows to determine the presence of a complex trauma. For this, the patient, lying on his back, with two hands, holds the thigh of the injured leg next to the knee joint. Then the victim tries to raise the shin without bending his knee. If he succeeds and the tibia does not move, the ligament is damaged.

3. Back slack test. In order to detect damage to the posterior cruciate ligament, it is also possible not to do x-rays of the knee joint. The technology of this research is simple, reliable and widely available. The patient should be asked to lie on his back and bend his knees at an angle of ninety degrees. If the tibia moves posteriorly, the ligament is damaged.

Instrumental studies of the joint

The most common method of examining bones is radiography. If the patient complains of joint pain after a fall, fever, swelling and bruising, it is advisable to check if there is a fracture there. The x-ray of the knee allows you to see bones, soft tissues and tendons. Looking at the picture, a trauma doctor can diagnose: fracture, dislocation, stretching, patellar injury, arthrosis, arthritis, swelling or cyst, osteoporosis or osteomyelitis. These are the most common diseases affecting the knee joint. Photos, of course, can be of different quality, rigidity and size, but for a specialist it is not difficult.

In order to exclude rheumatoid arthritis, degenerative pathology and joint trauma, you can conduct ultrasound. Another positive thing is that the patient does not need to undergo preliminary training (hunger, plentiful drink, etc.) before examining the knee joint. Its anatomy allows you to look inside the articular bag, see menisci, a surface covered with cartilage, bone formations.

The ultrasound allows you to look at the knee from all sides. For a clear picture you need to put the patient correctly:
- on the back with straight legs (the front and side walls of the joint are clearly visible);
- the legs are bent at the knee joints (menisci are visualized);
- in the position on the abdomen (for examination of the posterior joint wall).

Such a procedure can be performed in almost any medical and preventive institution.