Chondromalacia patellae: a system of classification.

Degeneration of the cartilage on the under surface of the patella is shown to be the most frequent cause of "internal derangement of the knee" (63%). The axial view of the patellofemoral joint in 4 angles of flexion constitutes the procedure of choice for diagnostic exploration of patellar cartilage with, perhaps, the restriction for the medial compartment where arthroscopy is probably preferrable. The information obtained from single contrast arthrography of the patellofemoral joint has contributed greatly to the understanding of the sometimes confusing problem of chondromalacia of the patella. It has given an anatomic basis to the patellar syndrome and has served as a basis for a precise typographic system of classification. From this, we have been able to correlate localization and etiology which has then allowed logical solutions to be proposed for each group, based upon biomechanical considerations in both the frontal and saggital planes of the knee.