Why do kneecap dislocations become a recurrent problem?
When the kneecap comes out of joint the first time, ligaments that were holding the kneecap in position are torn. The most commonly torn structure is called the medial patellofemoral ligament, or MPFL. This ligament secures the patella to the inside (medial) of the knee. When a kneecap dislocation occurs, something must fail to allow the kneecap out of the groove, and usually it is the MPFL. Once the MPFL is torn, it often does not heal with proper tension, and the kneecap can subsequently dislocate more easily. That is why recurrent dislocation of the kneecap occurs in a high percentage of patients who have this injury.
