If the hollow area where the kneecap rests is uneven or not deep enough it could cause a dislocation.

INJURY
Unstable Kneecap

ALSO KNOWN AS
Dislocated Kneecap

ABOUT
A normal kneecap fits into a concave surface in the femur (thighbone) where it joins the muscles in the front of the thigh to the tibia. The kneecap moves up or down as you bend or straighten the leg.

COMMON INJURY
If the hollow area where the kneecap rests is uneven or not deep enough it could cause a dislocation. A fall or sharp blow to the kneecap could also cause it to pop out of place.

DIAGNOSIS
Your doctor will assess your symptoms. Typical symptoms of an unstable knee are stiffness, swelling, knee cannot support your weight, kneecap slips to the side, pain in the front of the knee, cracking noises in the knee. Your physician will likely do a physical exam and have you straighten and bend your knee and walk on the troubled leg. X-rays might also be ordered.

NON SURGICAL TREATMENT
A dislocated kneecap needs a reduction, which is where it is properly set in place. Partial dislocations can be treated with braces and certain exercises, such as cycling, that can help strengthen the muscles that can keep the kneecap in place.

SURGICAL TREATMENT
Arthroscopic surgery can correct the damage under the kneecap and end of the femur that can occur from a dislocation. Continuous unstable kneecap may need surgery to remove tissue that pulls the kneecap out or realign and tighten tendons that can keep it in place.

Unstable Kneecap
Image courtesy of AAOS