The schematic drawing of the modality of measurement of Z angle. Point A was the lateral end of the posterior facet of talus. A straight line α was made through point A and parallel to subtalar joint. Straight line β was parallel to subtalar joint and located at the level just below sustentaculum tali in the axial view. Point B was the intersection of line β and the lateral wall of calcaneus. Angle Z is formed by two intersecting lines: line α and line AB.