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.
What can be done to treat a kneecap dislocation?
Traditionally, kneecap dislocations were treated by bracing a patient, and allowing the MPFL to heal. Unfortunately, bracing does not seem to be terribly effective, and no matter how long a brace is worn after a kneecap dislocation, the redislocation rate is still quite high.
In patients who have recurrent (repeat) dislocations, there are surgical options. The usual treatment is to loosen the lateral (outside) ligaments that pull the kneecap; a so-called lateral release. At the same time, the muscle of the medial side of the knee (the VMO) is advanced to pull the kneecap more centrally.
What about surgery after a first-time kneecap dislocation?
Recent interest has developed in preventing these recurrent dislocations. Each time the kneecap dislocates, the cartilage can be injured, and the ligaments can become more stretched out. Some surgeons are trying to restore the normal anatomy by repairing the MPFL after a first-time dislocation. This surgery is controversial, because not all patients who dislocate their kneecap will have another dislocation. However, some patients would rather have the ligament repaired in an effort to lower the chance of having this become a repeat problem.
