Three-dimensional joint surface orientation does not correlate with two-dimensional coronal joint line orientation in knee osteoarthritis: Three-dimensional analysis of upright computed tomography

•When joint line orientation of the knee was evaluated on the two-dimensional (2D) coronal radiography in our OA subjects, knee alignment (FTA) was expectedly correlated with 2D joint line parameters.•However, 3D joint surface orientation evaluated by the upright weight-bearing CT did not correlate with any 2D joint line parameters and FTA.•3D joint surface orientation was likely to be unaffected by OA severity, and 2D evaluation of knee alignment and joint line orientation is not accurate in the preoperative planning of TKA.