Bone · Knee

Patella

Patella

The patella is the kneecap, and it is a bone that grew inside a tendon — the quadriceps tendon wraps it and carries on below it as the patellar tendon. Its job is leverage: by holding the tendon away from the joint it lengthens the quadriceps' lever arm on the knee. It glides in a shallow groove on the front of the thigh bone as the knee bends and straightens, and most trouble here is about how it tracks in that groove rather than the bone itself.