Intramedullary instrumentation is currently considered as the standard technique for making the distal femoral cut in total knee arthroplasty. The purpose of this investigation was to determine the variance in the angle between the femoral mechanical axis (FMA) and the femoral anatomical axis (FAA). This angle was measured in 73 arthritic patients. The mean angle for varus knees was 7.7° (range 4°–12°). The mean angle for valgus knees was 5.8° (range 4°–7°). The difference between both groups was statistically significant. It is concluded that the FMA-FAA angle should be measured using X-rays and used on instrumentation jigs to avoid femoral malalignment in the coronal plane.