Paediatric flexible flatfoot is a very common condition which tends to improve over time in many children. During the period of its persistence, however, it can be quite painful and debilitating. The authors randomized patients to receive a customized arch support for 12 weeks or control (no insoles). Outcomes included radiographic outcomes, pain, function, stair ascent time, and overall mobility. Patients with customized arch supports had significantly better pain/comfort, physical health, stair ascent time, upper extremity and physical function, and transfer and basic mobility during the intervention period.