Flat Foot (Pes Planus)

A large share of the population has low arches and no symptoms whatsoever. Treating a painless flat foot because it looks wrong on an assessment mat is overtreatment, and we say so before selling anything.

In children, the arch develops through the early years and a flexible flat foot in a child who runs and plays without pain is normal 1. There is no good evidence that insoles create an arch: some studies report changes in foot posture, but they have methodological limitations and the effect remains uncertain 2. A Cochrane review found no support for orthoses in healthy children whose flat feet do not hurt 1.

Adult acquired flat foot — a previously normal arch that flattens, usually in middle age, with pain and swelling on the inner ankle and difficulty rising onto the toes on one leg — is tibialis posterior tendon dysfunction. Untreated it progresses from a correctable deformity to a rigid one.

This is the situation where early assessment matters most, because a deformity that has become rigid is a surgical question rather than a rehabilitation one.

Progressive strengthening of the tendon and the small muscles of the foot, calf flexibility work, gait retraining, and orthotic support where the foot needs offloading while it is being strengthened. Footwear advice does more than most patients expect.

A rigid flat foot — one that does not correct when the patient rises onto the toes — is a surgical question, and rehabilitation is planned around the operation rather than instead of it.

A flexible flat foot that forms an arch on tiptoe and causes no pain needs nothing. A rigid flat foot, a painful one, or an arch that has collapsed in adulthood is a different matter.

Adult-acquired flatfoot from posterior tibial tendon dysfunction progresses if untreated and is far easier to manage early. The single heel raise test — being unable to lift the heel on that leg alone — is the sign that matters most.

In the early, flexible stages there is some trial support for them, although it is limited. In a randomised trial of 36 adults with stage I or II disease, all participants wore orthoses and stretched for 12 weeks; pain and function improved in every group, and those who also did progressive resistance exercise improved more 3.

A systematic review of the three available randomised trials, 93 patients in total, found moderate effects on pain and disability when eccentric strengthening was added to stretching and orthoses, and described high-quality research as scarce 4. These trials measured pain and function rather than whether the arch continued to collapse, so they do not show whether exercise slows progression, which is why the shape of the foot and the single heel raise are reassessed as treatment continues.