Comparison of the foot kinematics during weight bearing between normal foot feet and the flat feet

Purpose: The purpose of this study was to clarify the difference in foot kinematics, including detailed analysis of the midand forefoot, between normal and flat feet. Methods: Forty-six feet of 33 young normal volunteers were participated in this study. All subjects were categorized two groups which were normal foot group and flat foot group. The fifteen color markers were mounted over the anatomical landmarks. Foot motion in a stance with the measurement foot forward, the body weight loaded on the forefoot as much as possible with the lower leg inclined forward and the entire plantar surface in contact with the floor was recorded using four hi-definition digital video cameras. All markers were manually digitized using the Frame-DIAS4 software program (DKH Co. Ltd, Tokyo, Japan). The three directional coordinates of each marker were calculated, and the three directional movements of each marker were compared between normal feet and flat feet using the Man-Whitney U-test. Moreover, discriminant functional analyses were performed on all combinations if significant differences were found between normal feet and flat feet. Results: Normal foot showed medial inclination with maintaining the arch structure, however flat foot showed that forward splaying with collapsed arch structure. Moreover, the forward movements of the cuboid and medial movement of the third metatarsal base may be key movements. Conclusions: It might be important for the treatment of flat feet to control the stability of the lateral longitudinal arch.