A dislocated kneecap occurs when the patella (kneecap) that sits over the front of the knee comes out of its groove at the end of the thigh bone (femur), coming to rest on the outside of the knee joint. This can cause stretching or tearing to the supporting ligaments and tendons. Normally, the kneecap glides smoothly over a groove in the joint when you bend or straighten your leg but if the kneecap is dislocated you may be unable to bend or straighten your leg. A dislocated kneecap is a common injury that can take around 6 weeks to heal. If you have dislocated your kneecap once it is far more likely to dislocate in the future.
Kneecap dislocation is not the same as knee dislocation.