PURPOSE: The purpose of the current study was to investigate the relationship between the angles made by the reference axes on the axial magnetic resonance (MR) images and to provide information for determining the rotational alignment of the femoral component in total knee arthroplasty. MATERIALS AND METHODS: We analyzed 194 magnetic resonance (MR) images to measure the posterior condylar angle, the condylar twist angle and the difference between the posterior condylar angle and the condylar twist angle. We then evaluated the relationship between these angular measurements. RESULTS: The condylar twist angle averaged 6.09degrees, the posterior condylar angle averaged 2.95degrees and the difference between the posterior condylar angle and the condylar twist angle was 3.14degrees. There were no differences in these angles based on gender and age. CONCLUSION: In the cases that the center of the medial epicondyle is difficult to clearly identify during TKA, the femoral rotational resection angle can be determined by subtracting 3degrees from the condylar twist angle.