The axis of motion for the subtalar joint is directed backward, downward, and laterally (Fig. 16-30). The degree of inclination and mediolateral deviation of the axis varies greatly among persons. The average deviation from the midline of the foot is 16°, whereas the average deviation from the horizontal is 42°. Because the axis of motion for the subtalar joint deviates from the sagittal plane and from the horizontal plane, movement at this joint involves combined eversion, dorsiflexion, and abduction or combined inversion, plantar flexion, and adduction. Note that pure abduction and adduction of the foot are movements that would occur about a vertical axis and that inversion and eversion occur about a purely horizontal axis. Inasmuch as the subtalar axis is positioned about midway between horizontal and vertical, it follows that movement about this axis would include elements of adduction–abduction as well as eversion–inversion.