The synovial folds of the patellofemoral joint: A dynamic study

Abstract

The synovial folds of the patellofemoral joint have been studied in five fresh cadaveric knees through a window cut in the patella. When the knee is extended, the superior part of the patellar articular surface lies on the synovium lining the supracondylar fat pad of the femur, which has a distal leading edge and a distal excursion of 2 to 3 mm. As the knee flexes, the contact area of the patella on the femur sweeps superiorly, and the inferior articular surface is covered by the alar folds of the infrapatellar fat pad which face towards one another, and the midline of the joint. On flexion beyond 90° the alar folds move away like a curtain opening, to face away from one another. The synovium lining the infrapatellar fat pad then lies on the medial facet of the patella.