Fig. (2) Measurement of the relaxed calcaneal stance phase angle (RCSP) and the neutral calcaneal stance phase angle (NCSP). A bisector is drawn on the posterior aspect of the calcaneus. a. The patient stands erect. The angle between this line and the vertical line is the RCSP. b. With the subtalar joint placed in the neutral position, the angle between the bisector and the vertical line is the NCSP. The difference between the RCSP and NCSP represents the extent of excessive foot pronation or supination.