Advancement of the tibial tuberosity.

Surgical modifications of the biomechanics of osteoarthritic and chondromalacic patellofemoral joints reduce the joint pressure by distributing pressure evenly along the articular surfaces. Forward displacement of the patella tendon lengthens the lever arm of the tendon. It also increases the angle formed by the forces exerted by the quadriceps muscle and by the patella tendon. As a result, the compressive forces transmitted from the femur to the tibia and from the patella to the femur are decreased. If the anterior tuberosity of the tibia is displaced forward and medially, the subluxated patella is brought back into the intercondylar groove and the weight-bearing areas of the patello-femoral joint are increased. Consequently the operation much reduces the compressive stresses in the joint. In osteoarthritis of the patellofemoral joint and in chondromalacia of the patella, surgical displacement of the patella tendon forward consistently relieved pain.