Biomechanical effects of foot orthoses in children with flexible flat foot; a systematic review.

Background: Flexible flatfoot, characterized by a collapsed medial longitudinal arch during weight-bearing, was a common pediatric condition associated with pain, balance deficits, and an increased risk of musculoskeletal complications. Foot orthoses were frequently prescribed, but their biomechanical effects in children had not been fully established. This systematic review aimed to synthesize evidence on the biomechanical effects of foot orthoses in children with flexible flatfoot. Methods: Following the PRISMA 2020 guidelines, four databases (PubMed, Scopus, Web of Science, and ProQuest) were searched from inception to July 2025. Eligible studies included randomized controlled trials, cohort studies, quasi-experimental studies, and cross-sectional studies that evaluated biomechanical outcomes of orthotic interventions. Due to heterogeneity, a narrative synthesis was conducted. Risk of bias was assessed using the Modified Downs and Black checklist. Results: Twenty-two studies (n = 844; mean age: 8.9 years; 52% male) were included. Orthoses reduced midfoot plantar pressure (up to -48.5 kPa), ankle inversion moments (-0.3 Nm/kg), and center of pressure displacement (-5 mm), while improving step length (+5 cm), balance, muscle activity, and radiographic indices (e.g., talonavicular coverage angle improved by 5°). Predictors of better outcomes included low navicular height (<1 cm), high arch index (>0.26), and higher pain scores (>3). Conclusion: Foot orthoses offered measurable biomechanical benefits in pediatric flexible flatfoot. Clinical use should be individualized and guided by objective assessment. Further high-quality RCTs with standardized outcome measures and longer follow-up are warranted.