Fig. 2

a Preoperative planning; α60 shows the correction angle calculated as the postoperative WBL passed through the 60% point of %MA. A hinge point is set to the lateral tip of intercondylar eminence. b Joint line convergence angle with varus stress X-ray. c Joint line convergence angle with valgus stress X-ray. β shows the value obtained by multiplying the sum of both JLCAs by 1.5. In this case, α60 was 11°, and β was 12° (varus- and valgus stress JLCA were 9° and − 1°, respectively). The value of β was greater than α60; thus, TCVO was performed to achieve the optimal alignment (d). JLCA: joint convergence angle. TCVO: tibial condylar valgus osteotomy