ORIGINAL INVESTIGATIONS: PDF OnlyKujala Urho M.; Kormano, Martti; Österman, Kalevi; Nelimarkka, Olavi; Hurme, Matti; Taimela, Simo; Dean, Peter B.Clinical Journal of Sport Medicine: January 1992 - p 21-26 Buy Abstract Patellofemoral congruity was analyzed using magnetic resonance imaging (MRI) in 54 women (10 normal knees, 10 with patellar chondromalacia, 14 with patellar subluxation, and 20 with patellar dislocation). The patellofemoral joints were imaged both sagittally and axially with the muscles relaxed and with the knee positioned in 0°, 10°, 20°, and 30° of flexion. The axial images were aligned through the midpoint of the patellar articular cartilage, and an index relating the position of the patella to the underlying lateral femoral condyle was measured. When the index was measured from images produced in knee extension (0°), the index significantly differentiated all the study groups from controls. In 20° and 30° of knee flexion, the differences between the groups were no longer as pronounced as in 0° and 10° of knee flexion. In knee extension, an index value <30% indicated normal, 30–50% indicated mild to moderate abnormality, and >50% indicated a distinct abnormality in the patellar position. Because our index takes into account both the patellar height and the tendency toward lateralization at full extension, it appears to provide a more reliable measure of patellofemoral incongruity than do standard radiographic measurements. © Lippincott-Raven Publishers.