[Synovial folds of the knee joint. The plica parapatellaris medialis].

Stimulated by arthroscopic insight into central abnormalities of the knee joint and by the large number of unexplained cases of "anterior knee pain", we have studied the synovia in more than 2000 contrast examinations of the joint. Surprisingly, and contrary to the views expressed in the literature, the clinically significant plica parapatellaris medialis was seen as frequently during pneumo-arthrography as during more complex procedures. Abnormalities in the synovial fold emerged as a discreet disease identified as the "medial shelf syndrome" and should be included in the differential diagnosis of causes of pain round the lower end of the femur and patella.