Fig. 3

Plain antero-posterior radiograph of a right knee with a Schatzker II, AO/OTA 41-B3.1 fracture. Line A represents the displacement of the tibial anatomical axis (Line D) to the femoral anatomical axis (Line C), measured at the best estimate of the joint line which is 1.5 cm proximal to the fibular head. Line B represents the femoral condyles width (the width of the femoral condyles at their widest point). To compensate for any magnification error, a unitless ratio was calculated in order to depict femoral displacement: Femoral Displacement Ratio (FDR) = Line A/Line B. In the case illustrated, FDR was 0.43/8.57 = 0.05