Fig. 2

Illustration of the new method proposed in this study. The axis-patella (AP) index is defined as “a1/b”. Measurement “a1” is measured from the lower pole of the patellar articular surface to the intersection point (T1) between the tibial shaft axis and its perpendicular line passing through the tip of the fibular head. Measurement “b” is the length of the patellar articular surface. The joint axis-patella (jAP) index is calculated by “a2/b”. Measurement “a2” is measured from the lower pole of the patellar articular surface to the intersection point (T2) between the tibial shaft axis and the joint line. The joint line height (JLH) is defined as the distance between the T1 and T2