Fig. 4

Anteroposterior (AP) motion from extension to flexion of the lateral (A) and medial (B) femoral condyles with respect to the tibial plateau for the 4 different types of implants compared to the native knee. A strong femoral rollback can be observed in the native knee. This rollback is partially imitated by the cruciate ligament retaining (GCR) and posterior stabilized (GPS) primary knees. No lateral femoral rollback can be observed in the rotating hinge (RSL) and total hinge knee (SSL). On the medial side the native knee also shows a discrete femoral rollback during flexion. This is, however, not imitated by any of the investigated prothesis. Of note, the position of the femoral axis with respect to the tibial axis in the sagittal plane of the hinged knees appears more ventrally throughout all degrees of flexion