Fig. 1

Measurement of parameters on the hip-to-ankle APS radiograph. A The midpoints of the femoral head, knee, and ankle joint were connected to form HKA. B LDFA was defined as the lateral angle subtended by the distal femoral condylar line and the femoral mechanical axis. MPTA referred to the medial angle between the tibial plateau line and the mechanical axis. C On the APS radiograph, CTFS_APS was recorded as the distance between the tangent line to the outermost joint edge of the lateral femoral condyle and the utmost margin of the lateral tibial plateau, and JLCA_APS referred to the angle between the distal femoral condylar line and the tibial plateau line