Long-Term Use of Anti-Pronation Insoles Enhances Inter-Joint Coordination in Individuals With Flat Feet

Flatfoot alters lower limb biomechanics and can negatively affect interjoint coordination during gait. Antipronation insoles are commonly prescribed to correct excessive foot pronation, yet their long-term effects on interjoint coordination remain unclear. This study aimed to examine whether prolonged use of antipronation insoles improves interjoint coordination in individuals with flat feet.

Twenty-four participants (12 with flat feet and 12 with normal arches) were included. Spatiotemporal and interjoint coordination parameters were evaluated under four gait conditions: normal gait (NG), posttest normal gait (PNG), walking with shoes (SH), and posttest walking with shoes (PSH). Gait kinematics and kinetics were recorded using a motion capture system and force plates. All participants completed a baseline gait assessment, after which the flat foot group (FFG) underwent a 6-week intervention with antipronation insoles. A follow-up gait assessment was conducted for both groups to determine the long-term effects of insole use. Interjoint coordination was analyzed using the vector coding technique.

Following 6 weeks of insole use, the flat-foot group showed phase-dependent changes in ankle-hip coordination, with lower coupling angles than controls during loading response and swing and higher angles during push-off under the normal-gait condition (p ≤ 0.01 and η²p = 0.28-0.33). Changes in ankle-knee and knee-hip coordination were smaller and generally limited to specific gait phases. Insoles produced an overall increase in coupling angles across conditions, reflecting these phase-specific effects. Spatiotemporal analysis showed longer single-support times in controls, longer double-support times in the flat-foot group with insoles, greater baseline stride length in controls, and no between-group difference in walking speed.

Long-term use of antipronation insoles improves interjoint coordination in distal lower limb joints and may contribute to a more conservative or steadier gait pattern in individuals with flat feet as reflected by phase-specific changes in spatiotemporal parameters. However, their limited influence on proximal joints underscores the need for complementary interventions, such as targeted rehabilitation exercises.