Fig. 1

Measured Coronal Knee Alignment Angles. The five angles were defined as the following: a The Hip–knee–ankle angle (HKAA): the angle between the mechanical axis of the femur and the tibia. The value of HKAA was defined as positive in varus alignment. b Lateral distal femoral angle (LDFA): the lateral angle between the mechanical axis of the femur and the distal femur joint line, which is defined as the connection of the lowest points of the medial and lateral femoral condyle. c Medial proximal tibial angle (MPTA): the medial angle between the mechanical axis of the tibia and the proximal tibia joint line, which is defined as the connection of the lowest points of the medial and lateral tibial plateau. d Angle between the femoral anatomical axis and the mechanical axis (AA-MA): the angle between the mechanical axis and the anatomical axis of the femur. e Knee alignment angle (KAA): the angle between the anatomical axis of the femur and the anatomical axis of the tibia in the short film of the knee. The value of KAA was defined as positive in varus alignment and as negative in valgus alignment. f Tibial joint line angle (TJLA): the angle formed by the parallel line to the floor and the proximal tibia joint line. If the two lines intersect with an angle on the lateral side of the leg, it is a medial open angle. If two lines intersect with an angle on the medial side of the leg, it is a lateral open angle. Lateral open angle is presented as a positive value, medial open angles as a negative angle. g Joint Line Convergence Angle (JLCA): the angle between the knee joint lines of the distal femur and proximal tibia