The knee is a complex joint of the body connecting the thigh bone to the shin bone. The main part of the joint is responsible for transmitting weight through the leg from the rest of the body to the foot.
Large strong muscles are required to control the movement of the joint, the most important of which is called the extensor mechanism comprising the quadriceps or thigh muscle. This muscle runs into a large tendon, which passes over the front of the knee before attaching onto a prominent bony tubercle on the front of the shin.
As the tendon passes over the front of the joint a large rounded bone is incorporated into the tendon, and this is called the kneecap or patella.