Summary:An angle within the femoral arch is defined, and its line is described in selecting the osteotomy site and the position of the fixation device in performing a femoral varus osteotomy. This neck metaphyseal angle was measured with varying degrees of rotation on seven pediatric femurs; it was also studied on 283 randomly selected hip radiographs. The angle varied 25‐40° in 90% of the patients and was not age related. The angle is stable within 5° as long as the landmarks, base of the great trochanter, and medial metaphysis of the femoral neck are definable (0‐30° of rotation).