The common name for the patella, the bone at the front of the knee joint, is the kneecap.
The patella is a flat, roughly triangular bone positioned in front of the knee. It sits within the quadriceps tendon and connects functionally with the patellar ligament, helping transmit force from the quadriceps muscles to the lower leg. This arrangement lets the knee extend and straighten more efficiently.
The patella also protects the front of the knee joint and helps guide movement as it glides across the lower end of the femur. It is the largest sesamoid bone in the human body, meaning it develops within a tendon. Babies are born with a cartilaginous patella that usually begins turning into bone at about age four.
A kneecap is not the same as the tibia, or shinbone, which lies below the knee, nor the fibula, the thinner bone beside it. Because the patella is exposed, direct blows can cause fractures, while twisting injuries can dislocate it.