Search strategy.

Individuals with flatfoot have impaired proprioception owing to ligament laxity and impaired tendons, which can result in poor balance. Foot orthoses (FOs) have been reported to stimulate plantar mechanical receptors and are used to manage foot overpronation in individuals with flatfoot. However, the results of the use of FOs to improve balance are inconsistent. In this systematic review and meta-analysis, we aimed to identify and investigate the effects of FOs on balance in individuals with flatfoot. Electronic databases were searched for articles published before March 2023. Peer-reviewed journal studies that included adult participants with flexible flatfoot and reported the effects of FOs on balance were included and classified based on the study design: randomized control trials (RCT) and non-RCTs. Four RCT studies were retained, and their methodological quality was assessed (mean, 63.2%; range 47.3%–73.1%: high), as were three non-RCT studies (mean, 54.1%; range, 42.1%–68.4%: high). Meta-analysis was performed by calculating the effect size using the standardized mean differences between the control and FO conditions. Transverse-arch insoles immediately improved static balance after use. However, no immediate significant effect was found for medial archsupport FOs, cuboid-posting FOs, or University of California Berkeley Laboratory FOs during the study period (2–5 weeks) when compared with the controls. The transverse-arch insole is the most effective FO feature for improving static balance. However, the high heterogeneity between study protocols contributes to the lack of evidence for the effects of FO on balance in people with flatfoot.