Adult Flat Foot

There are two major classifications of flat foot, congenital flat foot which is often asymptomatic and cannot be classed as a pathology, and acquired flat foot which occurs in adulthood secondary to some pathological condition. The causes of adult flat foot are many and include fractures or dislocations of the foot, abnormalities of the foot, neurological problems and arthritic conditions. The most frequent cause of this acquired form is a dysfunction of the tibialis posterior tendon, the tendon of one of the calf and foot muscles. Trauma to the area, inflammation or degenerative changes can all affect this tendon.

Pathological changes in the tendon of the posterior tibial muscle have been shown to occur more commonly in patients who take steroids, have high blood pressure, are overweight or diabetic and have had injuries or operation to their midfoot. In the group of joint conditions known as spondyloarthropathies the incidence of tendon dysfunction is higher, patients usually having a family history of joint problems. Since older people without particular medical problems can also suffer this condition, degenerative mechanical causes may also be important. In 10% of patients with rheumatoid arthritis this tendon pathology may occur.

The medial malleolus is the bony prominence inside the ankle and just below and in front of this is an area of compromised blood flow in which the tendon runs, which might contribute to the onset of degenerative changes in the tissues of this region. The tendon of the posterior tibialis muscle adds to the support of the medial longitudinal arch of the foot which is actively and passively supported by structures. The passive, static supporting structures are the longer and shorter plantar ligaments, the plantar fascia and the calcaneonavicular or spring ligament. The ankle bone, also called the talus, is prevented from slipping down and in by the spring ligament.

The tendon of the posterior tibialis muscle is the most powerful support for the medial arch of the foot. Muscle contraction through the tendon raises the inside of the medial arch of the foot and turns the foot inwards if it is not planted. Loss of this muscle function from a rupture or damage to the tendon deprives the foot arch of its most powerful supporting influence which allows the muscles which turn out the foot to act without restraint. The foot can then undergo three main postural alterations: flattening of the medial foot arch; turning out of the forefoot and turning out of the hindfoot area.

Because the ability to stabilise the rear part of the foot and make the forefoot into a stable and rigid platform has been lost, the patient’s gait pattern is altered and less efficient. Due to the loss of the powerful function of the tibialis posterior muscle this makes the main calf muscles, the gastrocnemius and soleus act further back in the foot rather than at the forefoot. The ankle bone is forced downwards and inwards which stretches the spring ligament, gradually leading to the inside of the ankle collapsing down as the joints assume new positions relative to each other.

On presentation with acquired flat foot symptoms patients typically report that the inner side of the ankle and foot suffers pain and swelling whilst weight bearing. They may notice a gradual reduction in the arch and observe that they are weight bearing on the inner half of the foot. Push off in walking becomes less easy as strength reduces and a limp may develop, with the soles of the shoes showing evidence of a change in the gait pattern. Physiotherapy assessment of a person with flat foot typically starts with a comparison of both feet and their arches in standing.

On observing a foot from behind it is usual to see the two lateral toes on the outside and if more are visible this indicates forefoot abduction. The angle between the line of the heel and the line of the lower leg will be measured by the physiotherapist assessing the foot, indicating the valgus angulation of the heel. Asking a patient with a normal foot to go up on tiptoe will show an internal movement of the heel as the calf muscle contracts.

Jonathan Blood Smyth is the Superintendent of Physiotherapy at an NHS hospital in the South-West of the UK. He writes articles about back pain, neck pain, and injury management. If you are looking for physiotherapists in Sheffield visit his website.