What is Patellar Dislocation?

Patellar dislocation is an injury in which the patella, or kneecap, is forced away from its central position between the femur, or thighbone, and the bones of the lower leg. This injury is often sports-related and is most common among children and adolescents. It usually presents a number of symptoms, particularly pain and swelling. Treatment for patellar dislocation typically includes physical therapy and, in severe cases, surgery.

Normally, the kneecap is suspended by tendons and ligaments over a cavity known as the patellofemoral groove, which is centrally located between the upper and lower leg. When the knee area is jarred or struck — a common occurrence in contact sports — the kneecap can be forced away from this groove, or dislocated. This abnormal motion can cause the ligaments which normally hold the kneecap in place to overstretch or even tear.

A number of symptoms usually accompany patellar dislocation. Foremost among these are severe pain and swelling in the knee area. Bruising is also common. Dislocation sufferers may also experience a feeling of instability in the affected leg, or the sensation that the knee is going to “buckle.”

Often, the patella will reposition itself shortly after dislocation. This may happen as a result of prodding in the knee area during injury assessment, or may occur spontaneously as the injured party extends the leg. Relocation may be accompanied by a popping or snapping sensation, followed by an immediate reduction of knee pain.

Although this repositioning may reduce or relieve pain, patellar dislocation can cause lingering complications in the knee area, and therefore sufferers should consult a physician even if their kneecap has spontaneously relocated. Most common among these potential complications is damage to the ligaments which surround the kneecap. In rare cases, fragments of bone may break away from the knee cap during movement. This condition can cause extensive damage to the knee area, and usually requires surgical treatment.

After the kneecap has been repositioned, most physicians recommend that patellar dislocation sufferers rest and ice the affected leg. The knee may be taped to temporarily stabilize the patella. After this initial rest period, many sufferers complete a course of physical therapy, which usually consists of exercises to strengthen both the patellar structure and the other leg muscles, which can then provide additional support to the knee. Surgery may be necessary if the patellar ligaments have been severely damaged, if dislocation reoccurs repeatedly, or if the kneecap has become fragmented.