Illustration of a posterior knee joint. Between the femoral condyles is the posterior cruciate ligament (PCL) with the anterior cruciate ligament ligament (ACL) partly visible. Menisci are load-bearing, reduce friction and create a concave surface for femoral movement. The ACL prevents excessive posterior displacement of the femur. The PCL prevents excessive anterior displacement of the femur. From Lizars, J. 1823 A system of anatomical plates of the human body. W. H.Lizars, Edinburgh.