The effect of excessive subtalar joint pronation on patellofemoral mechanics: a theoretical model.

Excessive compression of the lateral articular surfaces is frequently a major component of patellofemoral dysfunction. Many subjects exhibiting symptoms of this disorder have structural deviations throughout the lower extremity which combine to produce malalignment of the patellofemoral joint. Included in these malalignment factors is excessive pronation of the subtalar joint. Excessive rotation of the lower leg which accompanies subtalar joint pronation has been cited as a major contributor to patellofemoral dysfunction. Although the excessive rotation of the lower leg will disrupt the normal mechanics of the tibiofemoral joint, the specific link between tibial rotation and patellofemoral symptoms has not been established. This paper presents a theoretical model which describes the compensation that can occur at the tibiofemoral joint to deal with the excessive tibial rotation. The link between the tibiofemoral compensation and increased patellofemoral compression is delineated. Factors which determine whether this increased compression becomes symptomatic are discussed. J Orthop Sports Phys Ther 1987;9(4):160-165.