A tear of the kneecap tendon is a major complication. This tendon attaches from the thigh muscles to the shinbone, allowing you to straighten your knee. During the surgical procedure, in order to get into the joint, the tendon needs to be moved. If the tendon fits very tightly on the knee, the tendon 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.