Fig. (9) Long-leg standing radiograph six years after femoral and nine years after tibial lengthening: The frontal plane mechanical axis, which is drawn from the center of the femoral head to the center of the ankle plafond, passes slightly medial to the center of the knee joint indicating an optimal limb alignment. This perpendicular distance, also called mechanical axis deviation (MAD), is normally 8±7mm medial to the center of the knee joint.