kneecap (patella), saucer-shaped bone at the front of the knee joint it protects the ends of the femur, or thighbone, and the tibia, the large bone of the foreleg. The kneecap is embedded in the tendon tissue of the quadriceps femoris, a large thigh muscle. As the leg bends and straightens, the kneecap glides up and down in a groove of the femur. Dislocation of the kneecap is a common athletic injury, occurring when stress on the powerful extensor muscles that straighten the leg pulls the kneecap to one side. See skeleton .

The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.

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