M22: Disorders of patella

M22.0: Recurrent dislocation of patella

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.

In your case, your kneecap has come out of the groove in your thighbone (femur). This can happen as a result of very normal movements not involving any excessive force. In certain circumstances this happens regularly. For example, when the muscles around the knee are too weak or when the kneecap is an unusual shape. If the kneecap has been dislocated in the past it will get dislocated again more easily.

When the kneecap comes out of the groove in the femur, tissue around the knee can get damaged. The knee can also be painful or swell up.