Thursday, August 21, 2008

Anatomy Of The Knee


The knee is made up of bones, ligaments, tendons, cartilage, and a joint capsule, all of which are composed of collagen. Ligaments connect bone to bone. Tendons attach muscle to bone. Cartilage is the smooth, fibrous connective tissue covering bones that allows easy, gliding movement.



Collagen is the fibrous protein constituent of connective tissue present throughout the body. As we age, the most obvious sign of collagen breakdown is in the face, where it leads to the sagging that keeps plastic surgeons in business. Less obviously, however, collagen breaks down throughout the body and contributes to a variety of age-related injuries and conditions. These keep orthopedic surgeons in business. However, treatments and methods other than surgery may do a better job of preserving and rejuvenating the knee.

The knee joint is a link between the thighbone—the femur—and the two bones of the lower leg—the tibia (large and on the inside) and the fibula (small and on the outside). The attaching ligaments on the outer surfaces of the knee are the medial collateral ligament (connecting the tibia to the femur) and the lateral collateral ligament (connecting the fibula to the femur). The patellar tendon attaches the quadriceps muscles of the thigh to the tibia, enabling extension of the knee. Inside the knee joint, two ligaments stretch between the femur and tibia—the anterior cruciate ligament and, behind it, the posterior cruciate ligament. Covering the ends of the bones is articular cartilage, which provides a smooth surface to facilitate motion. Articular cartilage is so named because when bones move against each other, they are said to articulate. In the knee, auricular cartilage covers the end of the femur, the top of the tibia, and the back of the patella (the kneecap). In the middle of the knee joint are the menisci, which are collagenous disc-shaped cushions that act as shock absorbers.

Unlike a ball joint, such as the hip, which sits in a deep pocket (the acetabulum of the pelvis), the knee doesn’t have much protection from trauma and stress. It is designed to move mostly in one plane like a hinge. Because of this inherent limitation of movement, strong knee ligaments are extremely important for knee health.

Side-to-side stresses are controlled by the medial and lateral collateral ligaments; front-to-back motion is handled by the anterior and posterior cruciate ligaments, which ensure that the tibia doesn’t slide backward or forward in relation to the femur. When these ligaments become lax, or are torn, bone movement may become excessive and damaging, and painful arthritis can begin.

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