Although it is universally accepted that patellofemoral malalignment is the main cause of anterior knee pain and functional patellar instability in the active young, the question remains to be answered: what is the mechanism whereby patellofemoral malalignment produces pain and instability? Currently, there are two theories to explain the origin of pain and instability in patients with patellofemoral malalignment: the neural theory and the mechanical theory. Both theories are not exclusive, but complementary. We believe it is the neural factor that precipitates the symptoms in patients with certain mechanical anomalies who also subject the knee to overuse.