About the Knee

Parts of the Knee

Three bones form the knee joint: the femur, the tibia and the patella.

Femur
The longest and heaviest bone in your body is found in the thigh. The lower end of the femur has two curved projections called condyles, which are part of the knee joint.

Tibia
The tibia is the larger of two bones found in the lower leg. The upper portion has two smooth surfaces called tubersities or tibial plateaus, which form the lower portion of the knee.

Patella
Known as the "knee cap," this is a flat, triangular bone located in front of the knee.

Functions of the Knee

The knee is the largest joint in the body and is affected by arthritis more than any other joint. It is classified as a hinge joint because, like the hinges on a door, the motion allowed is back and forth. This allows you to bend your leg. The knee also has some side-to-side motion. One function of the knee is bearing your body weight while you stand or walk.

The knee, unlike any other joint in the body, depends almost completely on its surrounding ligaments for stability. The ligaments keep the bones from slipping, sliding or otherwise moving out of their proper position. The two most important sets of ligaments are the cruciate ligaments located in front and back of the knee, and the collateral ligaments located on the sides of the knee.