Patellofemoral Biomechanics

Patellofemoral biomechanics are influenced by the anatomy of the patella and trochlear groove and the forces applied to the patella through the quadriceps muscles, patellar tendon, medial and lateral ligaments, and retinacular structures. The normal valgus orientation of the knee causes a lateral orientation in the resultant force acting on the patella from the quadriceps muscles and patellar tendon. The trochlear groove provides the primary articular resistance to lateral patellar maltracking, while the medial patellofemoral ligament is the primary passive restraint. Lateral maltracking can contribute to patellofemoral pain related to overloading cartilage and lateral patellar instability. The primary anatomical factors that contribute to abnormal patellofemoral biomechanics are patella alta, a lateral position of the tibial tuberosity, and trochlear dysplasia. Injury to the medial patellofemoral ligament following a patellar dislocation also adversely influences patellar tracking. A patellar dislocation is typically initially treated conservatively, but several surgical options are available to treat recurrent patellar instability. Reconstruction of the medial patellofemoral ligament restores the passive resistance to lateral patellar maltracking, but does not address abnormal loading that contributes to patellar instability. Medialization of the tibial tuberosity can be performed to reduce the lateral force vector applied to the patella by the patellar tendon. Distalization of the tibial tuberosity can be performed to address patella alta and increase engagement of the patella with the trochlear groove. Trochleoplasty is an option to increase the articular constraint by deepening the trochlear groove.