Medial femoral torsion (MFT) can be corrected with derotational osteotomy. Derotational osteotomies can be performed in the proximal or the distal part of the femur. Similar results have been reported for these two procedures. The aim of this study was to evaluate the pathologic location of the MFT by measuring the degree of infratrochanteric and supratrochanteric torsion (STT) of the femur using computed tomography (CT) scans. The current study was carried out in patients with the chief complaint of an in-toeing gait because of the MFT. Sixty-seven patients were enrolled in the study. Forty-one patients (72 lower extremities) were included in the intervention group; 20 patients were included in the cerebral palsy (CP) group (35 lower extremities) and 21 patients were included in the developmental MFT group [developmental femoral torsional (DF) group, 37 lower extremities]. The control group included 26 patients (33 lower extremities) with uninjured limbs with a femoral or a tibial fracture. In this study, torsional angles [MFT, STT and infratrochanteric torsion (ITT)] were measured on CT scan using picture archiving and communication system measurement tools. To measure the STT and ITT, the most prominent points of the lesser and the greater trochanter were marked on CT scans; these two points were connected and were defined as the intertrochanteric line (ITL). The angle between the ITL and the axis of the femoral neck was defined as the STT. The angle between the ITL and the axis of the condylar axis was defined as the ITT. Two authors measured the MFT, STT, and ITT angles of each femur independently. The twisting of the femur had occurred in a different location for each case. In all groups, however, STT was reduced with increasing age; this change was statistically significantly. ITT of the each group showed a random distribution. The means of the ITT in the control group and the DF group did not change significantly, and that of the CP group tended to decrease with age. MFT of the control group and the DF group reduced significantly with age (P<0.05). The value of MFT in the CP group was steady, without a significant change with age. The pathology of MFT could occur differently in the supratrochanteric, infratrochanteric region, or for both sites in each patient. To avoid another lever arm disease after surgery, the correction of MFT should be performed in the correct position. In the CP group, derotational osteotomy could be performed safely at a younger age compared with the DF group. In addition, the distal femur is the preferable osteotomy site for older CP patients.