Fig. 3

Measurement of ATSLC and ATSMC. A For the lateral compartment, the sagittal plane scan that could visualize the most medial image of the fibula at the tibiofibular joint is selected. A best-fit circle (R) over the posterior edge of the lateral femoral condyle was drawn at the subchondral line, and a line tangent to the lateral tibial plateau (a) was also drawn. Then, 2 mutually parallel lines perpendicular to the lateral tibial plateau were determined. The first line (b) crossed the posterior edge of the tibia, and the second line (c) was tangent to the posterior margin of lateral femoral condyle’s best-fit circle. The distance between the two lines was measured as the ATSLC in extension. B The coronal image was utilized to help identify the appropriate sagittal plane. C A modified method was utilized when measured the ATSMC in extension. D The middle aspect of medial condyle was determined when visualizing on the coronal sequences to help identify the appropriate sagittal plane. (ATSLC anterior tibial subluxation of lateral compartment, ATSMC anterior tibial subluxation of medial compartment)