patellofemoral joint ( RID2759 ) Were it not for the discussion with the orthopedist, I would have assumed the LFC impaction injury was new. There is superimposed acute contusion in the same location at the anterolateral LFC. These anterolateral femoral impactions are typically the result of transient patellar dislocation. There is no defect or edema along the medial retinaculum/MPFL in this case, but the femoral trochlea is very shallow and there is an old osteochondral fragment in the posteromedial recess. I suspect she is a recurrent dislocator and her MPFL is stretched and incompetent. Does anyone know of an ethnic predisposition for patellofemoral instability? The orthopedist used to treat a large population of Koreans, among whom he thought the incidence was particularly high. I have seen the same among Indian females.