the fourth distinct movement of the human knee is the posterior backward migration of the femur with respect to the tibia during flexion this posterior migration is referred to as 34 rollback 34 in the human knee this motion is asymmetrical the lateral femoral condyle 39 s 34 rollback 34 is greater than that of the medial this movement can be quantified in terms of millimeters the mean rollback for the lateral femoral condyle is 24 mm whereas for the medial it is 10 mm naturally as with all movements of the human knee these are mean quantitative values but qualitatively relate to the anatomical phenomenon of 34 differential rollback 34 fig1 a 10d demonstrate this phenomenon fig1 a 39 10d 39 are a schematic side view of the medial femoral condyle in relationship to the medial tibial plateau as the femur flexes on the tibia the condyle 34 rollsback 34 to contact a progressional more posterior point on the plateau str1 this rolling distance traveled is approximately 10 mm in the mean average human knee fig1 a 34 10d 34 are a schematic side view of the lateral femoral condyle in relationship to the lateral tibial plateau as the femur flexes on the tibia the lateral condyle 34 rollsback 34 to contact a progressively more posterior point on the plateau str2 on.