Fig. 3

Measurement of TPD and FD. After the mFTA was measured, a perpendicular line was drawn at the level of the intercondylar notch with two perpendicular lines drawn from this line to the medial femoral condyle joint surface (line A) and lateral femoral condyle joint surface (line B). The difference between the two lines (A-B) was the FD. On the tibial side, the TPD was measured by drawing a perpendicular line on the mechanical axis of the tibia starting from the medial tibial plateau joint surface. The perpendicular distance from this line to the lateral tibial plateau was the TPD (line C). mFTA, mechanical femoro-tibial angle; FD, the difference between the medial and lateral femoral condyle levels; TPD, tibia plateau difference