Figure 1 Appearance and imaging of the patient’s bilateral knee joints.A shows preoperative left knee flexion; B shows the absence of left knee flexion contracture; C is the varus and valgus status of both knees in non-weight-bearing condition; D is weight-bearing full-length orthopantomogram of the lower limb, showing the left knee valgus and right knee varus deformity

Figure 2 Schematic diagram of preoperative left knee angle measurements.A is measurements suggesting a posterior tibial tilt(PTS) angle of 7°; B is measurement suggesting a femoral external rotation angle of 7°

Figure 3 Schematic diagram of intraoperative operations.A is unstressed condition of the gap in 0° neutral extension position before osteotomy; B shows simulated condition of the medial-lateral gap in the extension position after the force line adjusted to two degrees of exostosis and the amount of lateral femoral osteotomy increased; C shows the intraoperative testing of the medial-lateral tension by space again

Figure 4 Intraoperative medial-lateral gap balance detection and osteotomy operation in different positions.A shows the medial-lateral gap balance in the extension position; B shows the medial-lateral gap balance in the flexion position; C is intercondylar osteotomy; D is making tibial marrow cavity

Figure 5 Intraoperative testing of the flexion-extension joint space balance after prosthesis fitting

Figure 6 Schematic diagram of postoperative angle measurements related to the left knee.A shows postoperative force line in the presence of two degrees of valgus; B is X ray image of left knee at postoperative ortholateral position with posterior inclination of approximately three degrees