ABSTRACT
The medial femoral condyle is larger and extends more distally in comparison to the lateral condyle. The asymmetry of the femoral condyles and tibial plateaus allows for rotation of the tibia about its anatomical long axis during knee flexion. The centre of the knee lying just posterior to the weight-bearing axis describes normal lateral alignment. Studies using magnetic resonance imaging (MRI) of cadaveric and living knees has revealed that during flexion the lateral femoral condyle does rollback across the tibia, with relatively little rollback of the medial femoral condyle. The biomechanical function of the patella is to act as a pulley for the quadriceps and increase the power of the quadriceps by increasing the moment arm. Patella geometry is variable and can be grouped into three types according to Wiberg. There are static and dynamic elements to the biomechanics of the knee. Flexion-extension is controlled by the geometry of the femoral condyles and the polyethylene insert.
