Adult flatfoot

Adult flatfoot

As orthopedic specialists, we get referred a number of cases labeled as ‘Flatfoot’. While there are a number of conditions that give flat feet, the most common reason why an adult would develop a new pes planus, as we call it, is due to weakness (or insufficiency) of the main muscle responsible of keeping the inner arch of the foot.

Most cases we see will be nothing more than symmetrical flexible flatfeet, which is a variant of the norm; but if new onset pain associated with (generally) a single-sided new flatfoot deformity is the case, then professional opinion should be sought as timely simple treatment will hopefully defer surgical needs.

Reasons why one would develop weakness in this tibialis posterior muscle include trauma or repetitive strain injuries, but the exact cause is yet unknown. What we do know, however, is that obesity, female sex, diabetes, steroid use, and increasing age are the most common risk factors for developing this condition.

So what will the patient experience? It may start with a slight pain behind the inner ankle bone which is made worse with tip-toeing – which is, in fact, one of the bedside tests we do in clinic. The hindfoot (part of foot below the ankle joint) will start drifting outwards, which, together with the fallen inner arch of the foot is responsible for the typical appearance of a splayed, outward-drifted forefoot leading to the “too many toes sign” when seen from behind (as shown in the figure below). Neglected, or more advanced cases will start to develop arthritis of the ankle joints with worsening pains in the heel. The outer ankle bone may now start to hurt as it abuts the heel bone due to this severe hindfoot deformity.

Most cases, if caught early enough, will respond to simple measures such as orthotics (custom-made insoles) and physiotherapy. Injections to this tendon are not advisable because of the risk of tendon rupture. If these simple measures do not suffice, some reconstructive operations in the form of tendon transfer offer the best treatment outcome in the early stages of the conditions. Neglected cases that become stiff with arthritis will thereafter require more extensive surgery quite often necessitating fusion of the hindfoot to restore painless walking.

For more information on this topic, with more in-depth illustrations and anatomical explanations click here to visit the recommended plain English text by the American Academy of Orthopaedic Surgeons.

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