Current concepts on anatomy and biomechanics of patellar stability.

This review describes anatomic features of the patellofemoral joint that relate to the stability and function of the joint. The role of the geometry of the articular surfaces, particularly the trochlear groove, it's depth and orientation, are described. The stabilizing actions of the medial and lateral retinaculae, that tether the patella from either side to guide it into the trochlear groove in the early phase of knee flexion, are related to the specific structures, the medial patellofemoral ligament, and the fibers originating from the ilio-tibial tract laterally. The quadriceps muscles have different orientations, and converge onto the patella not only from either side but also from posteriorly, thus pulling the patella onto the anterior aspect of the trochlea. Finally, these local factors are discussed in relation to overall limb alignment, which leads to the mechanical logic of more extensive surgical procedures such as femoral rotational osteotomy or tibial tuberosity medialization.