M22: Disorders of patella

M22.9: Disorder of patella, unspecified

The knee joint connects the thigh to the lower leg. The knee joint is made up of 3 bones. These bones are the thighbone (femur), the shinbone (tibia) and the kneecap. The kneecap sits in a groove at the front of the thighbone.

The kneecap is embedded in a tendon of a muscle. This muscle pulls from the thighbone and from the hip to the shinbone and extends the knee. The kneecap helps this muscle to transfer force more effectively. The kneecap also reduces the friction between the tendon and the thighbone.