There are 206 bones in the human body, most of which do not exceed a few cubic centimeters in size. The most painful and massive bone in the body is the femur. Its structure allows us to walk straight and not fall. Through the knee joint, the femur connects to the tibia and fibula, forming a free lower limb.
Anatomy of the free lower limb
The human lower limb anatomy includes bones, muscles, ligaments, joints and fascia. This is if you take it seriously and in detail. But for this article, a small digression into the structure of the leg will suffice. So, the lower limb of a person is divided into the thigh, lower leg and foot.
The basis of the thigh is the femur. It is covered in layers by 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. Anatomymyofibrils allow them to stretch and contract, adjusting to the needs of the body.
The core of the lower leg is the tibia and fibula. Between themselves, they are connected by a joint and a connective tissue membrane in which the vessels pass. From above this design is covered with several layers of muscles that continue to the foot.
The ankle and foot are parts of the body that experience constant stress. A relatively small section of the sole holds the weight of the entire body (and sometimes it can reach up to three hundred kilograms). The foot consists of the calcaneus, tarsus, and metatarsus, which are covered with fasciae and muscles. Also, this area is abundantly supplied with blood, so that the muscles always have a supply of oxygen.
Basic structures of the knee joint
What is the anatomy of the human knee joint? For a first-year medical student, 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 lower leg position);
- nerves and blood vessels (nourish tissues and transmit information from the brain to the periphery);
- menisci (form the surface of the joint);
- ligaments (hold bones together);
All of the above components in a he althy person work harmoniously, as a single mechanism. But it is worth "breaking down" at least one component, and a smooth gait will no longer work.
Bones
The large bones of the knee joint are the femur and tibia. But besides them, there is also a small rounded bone, located separately from the rest. It is called the patella or kneecap. On the diaphysis of the femur are spherical elevations - condyles, covered with cartilage for better gliding. They are the upper part of the knee joint. The lower part is formed by the flat head of the tibia, also covered with cartilage.
The fibula is not long enough to form the knee joint. The anatomy of its head allows it to adhere to the tibia in such a way that the lower leg can be slightly rotated without getting fractures. The thickness of the cartilage covering the articular surfaces reaches five millimeters. It is necessary to reduce friction, as well as cushioning.
Cruciate ligaments
As mentioned above, in addition to bones and muscles, there are also ligaments of the knee joint. Their anatomy is very interesting, 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 (envelope) ligaments. Between the upper and lower articular surfaces are the cruciate ligaments. Topographically, the anterior and posterior ligaments can be distinguished, limiting excessive flexion and extension of the knee.
Ligaments are important elements of the joint. They stabilize him, make his gait firmer and allow him to avoiddislocations.
Menisci and their function
If you look at the picture of the knee joint, in addition to the bones, you will see two small formations. These are dense connective tissue formations - menisci. They are located between the femur and tibia.
Two main functions of the meniscus:
- increase the surface area of the joint for better weight distribution of the person;
- improve the stability of the knee joint along with the ligaments.
In order to imagine the role of the menisci, you need to imagine a ball located on a smooth flat surface. If there is nothing between the ball and the "plateau", then it will roll away. Nature does not tolerate emptiness, which means that the inside of the joint should not be empty either. Connective tissue fills the space between the articular surfaces, increasing their area and protecting them from excessive loads. Damage to the meniscus is fraught with inflammation of the joint and destruction of cartilage
Muscles
The extensor muscles descend from the front of the thigh to the knee joint. One of their ends is fixed to the femur or to the pelvis, and the other goes into the tendons and is woven into the joint capsule. The main one in this muscle group is the quadriceps. When it contracts, the leg extends at the joint.
The flexor muscles are located along the back of the thigh. They also begin at the girdle of the lower extremities, and end in the joint capsule in the form of tendons. When this group contracts, the leg flexes.
Nerves and blood vessels
Nerve fibres, arteries and veins wrap around the knee joint like a network. The anatomy of the vessels in this area is no fundamentally different from the rest of the body. The artery, accompanied by two veins, runs along the posterior surface of the joint, supplying the leg and foot with blood.
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 to the lower leg and foot. Thanks to him, the free lower limb receives sensitive and motor innervation.
Knee function tests
When a knee injury occurs, the traumatologist needs to find out, using physical and hardware methods, exactly what is damaged and how serious it is. To do this, it is not enough just to look at the knee joint.
1. Lachman test or drawer symptom. It is performed to determine the damage to the anterior cruciate ligament, if the picture of the knee joint could not be taken. 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 at the same time advances the lower leg forward. If movement is possible, then the ligament is damaged.
2. Non-contact test. If for some reason the doctor cannot touch the patient (for example, there is an obstacle in the form of a blockage or water between them), and an examination needs to be carried out, then this technique allows you to determine the presence of a complex injury. To do this, the patient, lying on his back, holds his thigh with both hands.injured leg near the knee joint. Then the victim tries to raise the lower leg without extending the knee. If he succeeds and the tibia does not move, then there is damage to the ligament.
3. Back sag test. In order to detect damage to the posterior cruciate ligament, it is also possible not to take an x-ray of the knee joint. The technology of this research is simple, trouble-free and widely available. The patient should be asked to lie on his back with his knees bent at a ninety degree angle. If at the same time the tibia moves backwards, then the ligament is damaged.
Instrumental examination of the joint
The most common way to examine bones is by x-ray. If the patient complains of pain in the joint after a fall, fever, swelling and hematoma, then it is advisable to check if there is a fracture. An x-ray of the knee joint allows you to see the bones, soft tissues and tendons. Looking at the picture, a traumatologist can make a diagnosis: fracture, dislocation, sprain, damage to the patella, arthrosis, arthritis, tumor or cyst, osteoporosis or osteomyelitis. These are the most common diseases that affect the knee joint. A photo, of course, can be of different quality, hardness and size, but for a specialist it will not be difficult.
In order to exclude rheumatoid arthritis, degenerative pathology and joint trauma, ultrasound can be performed. Another positive point is that the patient does not need to undergo preliminary preparation (hunger, copiousdrinking, etc.) before examining the knee joint. Its anatomy allows you to look inside the articular bag, see the menisci, the surface covered with cartilage, bone formations.
Ultrasound allows you to see the knee from all sides. For a clear picture, you need to correctly lay the patient:
- on his back with straightened 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 prone position (for examining the posterior wall of the joint).
This procedure can be performed in almost any medical institution.
