Kneecap Instability

By Keith W. Lawhorn, MD

Instability of the kneecap (also known as patellar instability) is a common problem affecting the knee joint. It occurs when the kneecap does not glide smoothly within the groove in the thighbone as you bend and straighten your knee.

Kneecap instability may indicate a subluxation, where the kneecap is partially out of the groove, or a full dislocation, where it is completely out of its normal position.

Genetic abnormalities, such as a shallow groove, an abnormally high riding knee cap or knocked-knee alignment may predispose people to kneecap instability. In addition, young athletes, especially females who play sports that involve twisting or pivoting have a higher risk of dislocation.

Common symptoms include apprehension, or “looseness” with the sensation that the kneecap is going to move outwards out of the groove. Patellar instability, especially recurrent instability can lead to damage of the surface cartilage resulting in pain, stiffness or swelling of the knee. With a dislocation, the knee often buckles, gives way, and is associated with significant pain.

Treatment depends on the type of injury, its severity, and other risk factors listed above. It's important that a qualified orthopaedic surgeon assess the problem to be sure the correct issues are addressed. Non-operative treatment includes bracing to immobilize the knee and allow ligaments to heal, physical therapy to strengthen surrounding muscles, and activity modification.

If these conservative measures fail to relieve symptoms, or if the knee continues to dislocate or subluxate, surgery may be necessary. Orthopaedic surgeons can offer surgical options that range from simple, direct patella realignment and ligament repair to more complex procedures, such as medial patellofemoral ligament (MPFL) reconstruction and tibial tubercle osteotomies, which show promise for patients with recurrent dislocations