A tear of the kneecap tendon is one of the major knee replacement surgery complications. This tendon attaches from the thigh muscles to the shinbone, allowing you to straighten your knee. During the knee replacement surgery, in order to get into the joint, the tendon needs to be moved. If the tendon fits very tightly on the knee, it can tear away from the bone when the knee is bent. If this occurs, the tendon must be reattached to the bone. If this fails, a cadaver tendon may be used to replace and reconstruct the damaged tendon.