Controversies and techniques in the surgical management of patellofemoral arthritis.

The patellofemoral joint is a complex articulation that remains a relatively uncommon topic in the orthopaedic literature. Most studies have been of cadavers, and there have been very few in vivo or clinical measurements1. The relative lack of interest in the patellofemoral joint is surprising given the fact that patellofemoral symptoms are relatively common and can be extremely debilitating. Abnormal mechanics of the patellofemoral articulation lead to abnormal pressures on the articular surface, pain, cartilage breakdown, and severe functional limitations secondary to anterior knee pain2. An understanding of basic concepts regarding patellofemoral joint kinematics, forces, and contact patterns will enhance the surgeon's understanding of the progression of patellofemoral arthritis. Furthermore, this understanding should ultimately allow the surgeon to choose the appropriate option for each stage of patellofemoral disease. The patellofemoral joint comprises the patella, the femoral condyles, and the trochlear groove. The patella is a sesamoid bone that acts to redirect the forces of the quadriceps to the distal part of the femur, functioning as a lever arm to increase the efficiency of the extensor mechanism. The femoral condyles have a dual articulation with the medial and lateral facets of the patella3. Additionally, almost 75% of people have a third articulating facet on the medial ridge of the patella that articulates with the medial femoral condyle after 120° of flexion4. The ridge of the lateral condyle is more prominent than the medial ridge on lateral radiographs of the knee. A deficient lateral condyle may be appreciated on lateral radiographs and may contribute to patellar instability. Between the condyles is the central sulcus, or trochlear groove. The quadriceps and the patellar tendon have a balanced, blended insertion and origin on the patella and generate the majority of forces acting on the patella. The …