Knee joint: structure in detail

Knee joint, the structure of which should be well known to every person involved in sports, the largest in the human body. It is formed by three bones. The structure of the knee joint of a man is due to its location. The ends of the bones forming its structure are covered with a very dense cartilaginous tissue of up to 6 mm thickness. This provides one of the main functions of the joint - shock absorption when walking.

Knee joint, structure

The photo shows us the main structures of this joint: muscles, bones, menisci, ligaments (cruciform), nerves and blood vessels. We begin to consider its structure with bones. The joint is formed by three bones. Two long ones are tubular, tibial and femur. The third is the patella. It is round in shape and very small. It is located in front. The femur below forms condyles - protuberances covered with cartilage. These protrusions contact the so-called tibial plateau, which consists, in turn, of two halves. The trochanter moves in the groove-shaped depression that formed the condyles. This notch is also called patellofemoral. The fibula is located laterally from the tibia. In the formation of the knee joint, it does not participate.

The structure and significance of cartilaginous tissue

The function of this fabric is in damping the shock load, reducing the frictional force during movements. It is necessary where two bone surfaces rub against each other. Articular cartilage is very tight. In the knee joint, it covers not only the ends of the femur and tibia, but also the surface of the patella. Cartilage tissue can be of several kinds. In the knee joint - hyaline. A feature of this tissue is a high water content in the intercellular substance. This provides elasticity and helps protect from knee joint damage.

The structure of ligaments and meniscuses

Dense connective tissue formations, fixing the ends of bones, are called ligaments. In the case of the knee joint, its capsule is strengthened by two such structures from the outside, medial and lateral. And two from inside - anterior and posterior cruciform. They limit excessive movements in the anteroposterior direction, preventing it from slipping relative to the femur. All knee ligaments are extremely important for its stable functioning. Between the femoral and tibia there are two other formations, called menisci. They can also be called cartilage, although their structure differs from the structure of hyaluronic, covering the joint surfaces. Menisci fill the space between the tibial plateau and the joint end of the femur.
They seem to serve as an elastic gasket, redistributing the weight. Without them, all of its gravity would be concentrated at one point on the tibial plateau. Two kinds of meniscuses (medial and lateral) are connected by a transverse ligament. Lateral (external) less often damaged due to its greater mobility. The inner (medial) meniscus is located near the inner lateral ligament and has a lesser lability. This is due to his frequent traumatization. In the center of the meniscus is thicker than around the edges - this forms a small hollow on the tibial plateau and makes the joint more stable. If there were no ligaments, we would have a much greater imbalance of the lower limb and would often injure the knee joint. The structure of the supporting elements of the knee ensures its stability

Synovial bags

They lie along the muscles and tendons. The largest - the patella (under the tendon of the quadriceps), it almost does not communicate with the joint cavity. Behind is a deep podnkolennaya bag, in the thickness of the joint - a few more smaller ones. When filling some of them with intra-articular fluid, cysts can form.

Muscles involved in flexion and extension of the joint

The quadriceps muscle is located on the anterior surface of the thigh. When it is cut, the leg in the knee joint is unbent. The patellar lies in the thickness of the tendon, serving as a fulcrum and changing the direction of movement if necessary. It increases the strength of the said muscle. Crushers of the shin (on the back of the thigh and near the knee) bend the leg in the knee joint.

Innervation

Consider the popliteal nerve. It is the largest of those located on the back of the joint. This nerve is a branch of the ischium. It provides a sensory and motor innervation of the joint capsule. Above the joint, it is divided into the tibial and peroneal nerves. They are worth mentioning, because with a knee injury they are often damaged. Also behind the capsule innervates the occlusive nerve. Some branches of the tibial nerve provide sensitivity to the posterior part. The fibular innervates the posterior and anterior surface. This is due to the fact that in the body there are few such mobile formations as the knee joint - structure and innervation with a large number of overlap zones provides high sensitivity.

Blood supply

The extensive vasculature surrounding the knee consists of four large arteries that are interconnected and form vascular plexuses (such networks around 13 on the surface of the joint) and inside it. The first and largest artery is the femoral artery. Popliteal, deep and anterior tibia slightly smaller. All of them develop collateral circulation in the event that one of the vessels is bandaged. The anatomical structure of the popliteal artery can easily be represented by dividing it into three sections. The first is the uppermost one. Betting is best done at the second level. The superficial veins in the region of the knee joint are arranged in two layers. The deeper is represented by a large saphenous vein. Superficial - a venous network from an additional one. The latter is not found in every person. A small saphenous vein leaves the posterior surface of the knee joint. Sometimes it goes one barrel, and sometimes two. The site of its confluence also varies, but more often falls into the popliteal.