Use of the longitudinal arch angle to predict dynamic foot posture in walking.

To determine whether differences exist in the longitudinal arch angle based on sex or extremity, the longitudinal arch angle was assessed in 21 men and 21 women using a digital image of the medial aspect of each subject's feet. The image was obtained with the subject in relaxed standing posture and in maximum internal rotation of the lower leg. To determine whether the longitudinal arch angle could be used to predict dynamic foot posture during walking, 50 different subjects were asked to walk across a 6-m walkway while the medial aspect of each foot was videotaped. The longitudinal arch angle was digitized from digital images obtained at midstance for three walking trials. No differences in the longitudinal arch angle were found based on sex or extremity. The longitudinal arch angles obtained in the static positions of relaxed standing posture and maximum internal rotation were highly predictive of dynamic foot posture at midstance during walking. Relaxed standing posture and maximum internal rotation significantly contributed to explaining more than 90% of the variance associated with the longitudinal arch angle position at midstance during walking. These results validate use of the longitudinal arch angle as part of the foot and ankle physical examination.