Fig. 1

TT-TG and TT-PCL measurement methods. Line 1’ was drawn through the deepest point of the trochlear groove and perpendicular to the cortical edge of the bilateral posterior condyle (line 1). Line 2’ was drawn through the tibial insertion of the posterior cruciate ligament and perpendicular to the posterior edges of the proximal tibia. The distance between the line through the top of the tibial tubercle (line 3’) perpendicular to line 1 and line 1’ under the overlaid images was defined as tibial tuberosity-trochlear groove (TT-TG) distance. The distance between line 3’ perpendicular to line 2 and line 2’ under the overlaid images was defined as tibial tuberosity-posterior cruciate ligament (TT-PCL) distance