REAR FOOT INVERSION EVERSION DURING GAIT RELATIVE TO THE SUBTALAR JOINT NEUTRAL POSITION/

Clinicians often fabricate foot orthotic devices at the subtalar joint neutral position (STNP) to mimic the position of the rear foot during midstance. However, rear foot motion during gait, relative to the res ting standing foot position, not the STNP, is often reported in the li terature. The motion of the rear foot relative to a valid estimate of the STNP is unknown. In this study, six experienced foot care speciali sts manually placed the rear part of the feet of nine subjects at the STNP seven or eight times to obtain a valid estimate of each subject's STNP. the worst-case mean and 95% confidence interval of the STNP est imate for any one subject was 0.0 degrees +/- 0.7 degrees. These nine subjects then walked on a motor-driven treadmill, set at 0.89 meters/s ec, and three-dimensional estimates of each subject's rear foot invers ion/eversion motion were obtained, then averaged over 6 to 26 strides. For most subjects, the rear foot was always everted during stance wit h mean and standard deviation maximal eversion (7.2 degrees +/- 1.2 de grees) occurring at 44% of the total gait cycle. The inversion/eversio n orientation during swing was characterized by 1 degrees to 2 degrees of eversion, with a small amount of inversion in early swing. These f indings have implications for the fabrication of foot orthoses, since the rear foot is rarely near the STNP during stance.