It is a problem faced by a few adolescents or adults that is difficult for them to describe and leads to anterior pain and/or fear that the kneecap (patella) will pop out of place on certain activities.

How Common: It is difficult to gauge the number of cases of kneecap instability because not everyone goes to their doctor, especially if symptoms are more benign.

Average patient: A knock-kneed adolescent female dancer with flat feet.

Cause: Twisting/pivoting/cutting movements with the knee out straight may lead to symptoms of instability or the kneecap popping out (dislocation).

What to do: If the kneecap pops back in (self-reduces) without any manipulation, then this injury is not an emergency and can be seen at the knee clinic. Many patients have recurrent bouts of dislocation that relocate spontaneously. In these cases, icing and immobilization (with the knee straight) can be done initially. However, a kneecap that remains dislocated needs to be treated urgently.

Severity of injury: If a piece of cartilage is knocked off during the dislocation, this is a serious problem that usually requires surgery. If the patient has a high-riding kneecap (patella alta), a flat distal femur (trochlear dysplasia), or a significant tear of the MPFL ligament that holds the kneecap in place on the inside of the knee, there is a much higher risk of another dislocation.

Treatment options: Most cases with anterior knee pain and first-time kneecap dislocations can be treated with physical therapy. In patients who have significant or recurrent instability, surgery is recommended. Surgery can range from soft tissue (ligament) repair or reconstruction to osteotomy (cutting and moving bone to change alignment) plus MPFL ligament reconstruction.

Expected result: About 90% of patients are able to return to activities after surgery. Those who have persisting issues usually have some arthritis under the kneecap. This is a consequence of repeated kneecap dislocations in the past.

Return-to-activity timeline: Non-operative treatment of a kneecap dislocation usually lasts for 6-8 weeks. Surgical treatment usually requires patients to be partial- or non-weight bearing for 6 weeks. They then have to work on recovering their movements and overall strength. A complete return to sports and dancing is usually achieved five to seven months after surgery.