Comparison of foot kinematics and ground reaction force characteristics during walking in individuals with highly and mildly pronated feet.

Background: Individuals with highly pronated feet (PF) are more prone to lower extremity injuries than those with mildly PF. However, whether foot kinematics and ground reaction force (GRF) characteristics differ according to the severity of PF deformity is unclear.

Research Question: Are there differences in foot kinematics and GRF characteristics during walking between individuals with mildly PF and those with highly PF?

Methods: Ten individuals with mildly PF and 10 with highly PF (six-item foot posture index scores: 6-9 and 10-12 points, respectively) participated in this study. A three-dimensional motion analysis system measured participants' foot kinematics and GRF characteristics during gait trials.

Results: Participants with highly PF exhibited significantly lower medial longitudinal arch heights than those with mildly PF from 0 % to 90 % of the stance phase (p < 0.05). No significant differences were observed in any of the angles between the foot segments. Additionally, participants with highly PF exhibited significantly larger posterior GRF than those with mildly PF from 2 % to 7 % of the stance phase (p < 0.05). Participants with highly PF also exhibited significantly larger anterior GRF than those with mildly PF, from 62 % to 82 % of the stance phase (p < 0.05).

Significance: The results of this study suggest that the more severe the PF deformity, the more inefficient the foot ground force transmission, and the stronger the load applied to the foot. These results may be related to the higher incidence of lower extremity injuries in individuals with highly PF than in those with mildly PF.