The knee joint is made up of three bones: the thigh bone (femur), the shin bone (tibia) and the kneecap (patella). The patella is located on the front of the knee, and is attached primarily to the quadriceps (quad) muscle and the tibia. It facilitates knee extension by transmitting the high forces from the quad muscle to the tibia, and is critical in enabling activities like walking, running and stairclimbing. To function properly, the patella needs to be able to glide in an up-and-down direction, without excessive side-to-side motion. This side-to-side stability is achieved by the unique bony anatomy of the back-side of the patella and an associated groove on the front of the femur which constrains the patella, in a wheel-in-a-rut fashion. In addition, ligaments on the inside and outside of the bone, and surrounding muscles play an important role in patellar dynamic stability and mechanics.

Patellar instability is a condition that occurs when the kneecap comes out of the groove and displaces to the side. If the displacement is complete, a patella dislocation occurs; a partial displacement is called a subluxation. This can occur in an acute traumatic episode, such as a sudden twisting injury to the knee, but commonly, patellar instability occurs in the absence of an injury, in a patient who has an anatomic predisposition based on knee anatomy that is inadequate in providing the necessary constraint and stability to the patella. That can include a shallow groove, loose ligaments, weak muscles, aberrant alignment of the lower extremity, among others.

Patients with a patellar dislocation report obvious deformity and painful displacement of the kneecap relative to its normal position. Sometimes a “giving out” sensation is felt during subluxations, and pain and swelling occur. Typically, however, patients do not complain of pain between instability episodes.
The diagnosis of patellar instability is made by a combination of the patient’s history, the findings on physical examination, and imaging studies, which may include an X-ray, a CT scan, and possibly an MRI.
Treatment for patellar instability depends upon the nature of the event (dislocation versus subluxation), the number of episodes experienced, the presence of anatomic predisposing factors for patella instability, associated injuries in the knee, and the response to previous treatments. In first-time dislocation events, typically conservative treatment, including short-term immobilization and bracing are employed. Physical therapy is critical in helping regain muscle strength to restore dynamic stability of the patella.

Despite these treatment modalities, the rate of recurrent instability episodes can reach 50%. For patients who suffer from debilitating recurrent instability episodes that have failed to respond to non-operative treatment measures, surgical treatment may be considered. The type of the surgery depends upon the quality of the soft tissue stabilizers as well as the patient’s bony anatomy. The surgery may either be a soft tissue procedure, a bony procedure, or a combination of both.

At Oceana Sports Medicine and Orthopaedic Center, Dr. Aboka performs minimally invasive Arthroscopic Patella Instability Surgery, customized to each patient and utilizing cutting edge approaches and instrumentation, facilitating a return to an active lifestyle.