To assess the reliability of the landmarks for the rotationally neutral alignment of the tibial component in total knee arthroplasty for Japanese patients, the rotational position of the medial ⅓ of the tibial tuberosity relative to the femoral epicondylar line (Angle TT) and that relative to the center of the ankle (Angle TT-AA) were measured in 24 knees with medial femorotibial osteoarthritis and in 28 normal knees by computed tomography. Angle TT-AA shows the degree of medial torsion of the tibia. The range of Angle TT and that of Angle TT-AA each was greater than 40°. The position of the tibial tuberosity and degree of medial torsion of the tibia varied by individual. In patients with severe medial torsion, the internal rotation of the foot is extreme if the medial ⅓ of the tibial tuberosity is used for the rotationally neutral alignment of the partially constrained tibial component. In the treatment specifically of patients from East Asian countries, medial torsion of the tibia should be taken into account in total knee arthroplasty to ensure proper patellar tracking and proper rotation of the foot in knees with medial femorotibial osteoarthritis.