Fig. 1

a Plain AP radiograph of a patient’s left knee from the sample showing how the LEJL and PTFJJL distances were calculated. The horizontal line is the joint line achieved after the surgery. The perpendicular above this line is LEJL and the perpendicular below this line is PTFJJL. Both these distances are nearly equal. b Sketch diagram of a left knee showing how the LEJL and PTFJJL distances were calculated. The horizontal line is the joint line (red) of the knee. The perpendicular above this line is LEJL (blue) and the perpendicular below this line is PTFJJL (green). Both these distances are nearly equal