Magnetic resonance imaging was used to quantify in vivo patellofemoral joint contact area
and to determine if contact area is affected by quadriceps muscle contraction. Ten subjects
without pain (six women, four men) had their right patellofemoral joint imaged. Cartilage-
enhanced, axial plane images were obtained at 0, 20, 40, and 60 knee flexion under
quadriceps loaded (contracted) and quadriceps unloaded (relaxed) conditions. Medial and
lateral facet contact area measurements were obtained on each image, and then summed …