The only true measurement of the pelvifemoral relationship is by the determination of the angle between the axis of the femur and a fixed line of pelvic reference.
Four new pelvifemoral angular relationships are described: two in the sagittal plane, the pelvifemoral angles of extension and of flexion; and two in the coronal plane, the co-pelvifemoral angles of abduction and adduction.
In the sagittal plane, motion can be measured by the pelvifemoral angle, the angle which opens downward and backward and is formed by Nélaton's line and the femoral axis. In maximal extension, the pelvifemoral angle of extension is 50 degrees. Any increase in the angle is indicative of a flexion contracture, measured by the amount that the angle exceeds the normal value. In maximum flexion, the pelvifemoral angle of flexion is 125 degrees. The total range of flexion and extension at the hip joint is 75 degrees.
In the coronal plane, motion at the hip joint can be determined by measuring the angle between the mechanical axis and the line drawn on the skin between the two femoral heads.