Foot kinematics and running dynamics in children and adolescents with flexible flatfoot

Flexible flatfoot (FFF) is prevalent in children and adolescents, often leading to pain and limited sports performance. Running poses unique challenges for individuals with FFF due to altered biomechanics, which may increase discomfort and injury risk. While adult studies highlight running-related foot dynamics, research on children and adolescents with FFF remains limited.

How do running dynamics differ between children and adolescents with FFF and those with normally developed feet (NF), and how does running type (rearfoot vs. forefoot) influence these dynamics?

This study included 84 children and adolescents (7-17 years) with FFF and 53 with NF. Participants underwent clinical assessments and instrumented gait analysis, capturing kinematic and kinetic data during barefoot running at self-selected speeds. Analyses examined the relationship between passive ankle dorsiflexion and running type, as well as foot shock absorption during impact and propulsion during push-off. Two-factor ANOVA compared foot conditions and running types.

FFF participants showed reduced passive ankle dorsiflexion, especially in habitual forefoot runners, with forefoot running less common in the FFF group (31 %) compared to NF (53 %). Forefoot runners exhibited greater rearfoot eversion excursion and velocity, but these differences were not significant between FFF and NF. Rearfoot runners demonstrated higher peak loading rates across both groups. FFF participants also had lower ankle strength, hindfoot inversion velocity at push-off, and generated reduced ankle moments and energy for propulsion compared to NF.

This study identifies biomechanical differences in individuals with FFF using a forefoot strike pattern, which may influence loading patterns. Although injury risk was not directly assessed, future research could explore whether improving ankle strength and flexibility may help mitigate potential disadvantages in FFF.