Patellar dislocations are the most common dislocations in the body. These are often traumatic, although in some patients a spontaneous dislocation can occur. The risk factors for patellar instability include a shallow trochlear groove, a tight lateral retinaculum, increased valgus alignment of the lower leg, an increased Q-angle, and generalized ligamentous laxity.
The patellar dislocation causes pain and swelling, and may also cause damage to the joint surfaces as the patella moves out of place. This may result in some chondromalacia in the patellofemoral joint, and sometimes an osteochondral fracture or osteochondral loose body.
Generally an initial patellar dislocation is treated conservatively, with a strengthening program and knee support. Many patients will be able to do well without further dislocations if they can maintain their quadriceps strength. The younger the patient age at the time of the first dislocation, the higher the risk of recurrent dislocation. Patients involved in cutting, pivoting and twisting activities are also more likely to sustain a recurrent patellar dislocation. Recurrent episodes of instability not only affect performance, but may also lead to further damage to the knee joint.
Generally recurrent patellar dislocations are treated with surgical stabilization. If the patient sustains a significant fracture of the patella or a loose body is present, then surgery is generally performed to remove the loose body and/or to stabilize the fracture. Surgical options include arthroscopy with lateral retinacular release alone, and/or repair of the medial retinaculum with or without lateral release, and a distal re-alignment.
