Last evidence check March 2010

Low-arched or “flat” feet are usually normal variants of foot posture and require no interference.

Some feet simply have a low arch, but have neutral rotational and coronal plane alignment.

Others are “flat” because the hindfoot and forefoot are rotated with respect to one another more than is usual. The subtalar joint is more pronated than usual, so the hindfoot is in valgus and the Achilles tendon may be tight. The forefoot is abducted and supinated at the midtarsal joint, so that the neck of the talus, which is normally in line with the first metatarsal in both transverse and sagittal planes, comes to point below and medial to the first ray. Because the hindfoot pronation and forefoot supination are balanced in most people, the foot sits plantigrade but the head of the talus in the medial border of the foot is low and the foot appears flat. This is the “overpronated” or “planovalgus” foot – but it must be emphasised again that such feet are usually asymptomatic, and there is no evidence that they are at a predictably high risk of future symptoms if not “treated”.

It should be appreciated that the “overpronated” foot is simply exhibiting an exaggerated version of the posture the foot normally adopts in early stance phase of gait. At initial heel contact, the heel is usually neutral or slightly varus, but the tibia rotates internally as the body begins to pass above the foot and this rotates the talus internally. Through the “torque converter” function of the subtalar joint, the subtalar joint becomes pronated and the heel moves into valgus. Increasing weight transfer through the foot tends to press down on the arch. In the normal foot, the static restraints, especially the plantar fascia but also the plantar, spring and deltoid ligaments and the joint capsules, restrict the pronation of the hindfoot and the tendency of the forefoot to dorsiflex. The leg moves over the foot in mid-stance, the tibia begins to rotate externally and the previous rotation is reversed. However, the foot may remain pronated for an unusual length of time, or even the whole of stance phase, if:

There is some evidence that a foot which remains in the pronated position for an unusual proportion of the stance phase functions less efficiently as a propulsive lever in late stance phase. There are also theoretically plausible mechanisms by which a variety of foot pathologies, such as hallux valgus, hallux rigidus, interdigital neuromas, tarsal tunnel syndrome and tibialis posterior tendonopathy may arise progressively out of such a foot. There is a body of thought influenced by Root which proposes active treatment of many such feet to influence future pathology as well as current symptoms. However, there is little empirical evidence that overpronation is so directly linked to such pathological conditions of the foot, or that early biomechanical intervention alters the natural history or is cost-effective. A lot of research is needed to clarify the relationship of overpronation and specific foot conditions, but most of it requires very long follow-up.

There are also congenital foot conditions which produce a flatfoot appearance without the effects of gait:

Clinically the main distinction is between:

Clinical assessment of a patient with flat feet is aimed at:

Management often consists solely of reassurance and advice to pursue normal activities. If the patient has symptoms which may be helped by orthotic treatment, this should usually be under the supervision of a podiatrist or orthotists who can produce and manage devices. Surgical involvement is not usually required. The most important team member is the one who can restrain more therapeutically aggressive colleagues from interfering with normal feet!