An abnormal lateral position of the tibial tuberosity causes lateral malalignment of the patella or objective patellar instability. When lateral patellar malalignment leads to chronic pain with or without instability, there is frequently an associated cartilage lesion. Magnetic resonance imaging can be used to evaluate the increased tibial tubercle-trochlear groove distance and any associated cartilage lesion. If there is a cartilage lesion on the distal or lateral patellar facet related to chronic lateral malalignment, an anteromedialization osteotomy will realign the extensor mechanism and help to unload the damaged articular cartilage. The surgical technique of anteromedialization osteotomy is described.