Acquired Flat Foot Posted By : Jonathan Blood-Smyth

Flat footedness is divided into acquired flat foot which is a condition which develops after we have attained maturity and congenital flat foot which is a common condition and often not of pathological significance. Adult flat foot has many potential causes which include dislocation and fractures, foot abnormalities, arthritic changes and neurological conditions. The commonest cause however of this foot problem is a dysfunction of one of the foot tendons, the posterior tibial muscle tendon. The methods by which the tibialis posterior tendon malfunctions are varied and ascribed to degeneration, inflammation or trauma.



Studies of this condition have revealed that it is more common in groups who are obese, diabetic, hypertensive, on steroid medication or had previous trauma or operations to the mid part of the foot. Patients with arthritic conditions, often called spondyloarthropathies, have typically a family history of psoriasis or inflammatory conditions and have a higher incidence of this condition. Older people without specific medical problems are also seen, pointing to a mechanical cause secondary to age related degenerative changes. This tendon problem is moderately commonly seen in patients with rheumatoid arthritis.



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 most important active or dynamic supporter of the medial arch is the tendon of the tibialis posterior muscle. As the muscle contracts it lifts the inside of the medial foot arch and turns the foot in if it not on the ground. If this muscle function is lost due to damage or rupture of this tendon then the foot loses its major arch support and inward turning action, allowing the outward turning muscles to act without opposition. This results in the foot suffering three main changes to its postural balance: the medial arch flattens; the front of the foot turns out and the rear of the foot turns out also.



All these changes lead to a loss of the ability of the rearfoot and the forefoot to be a rigid and stable platform which changes the patient's pattern of gait, making it less efficient. The tibialis posterior muscle has a powerful function and once this is reduced or lost the gastrocnemius and soleus, the main calf muscles, perform their action further back in the foot than normal. The talus or ankle bone is then moved inwards and down, stretching the spring ligament and gradually allowing the medial foot arch to lower as the joints move into different relationships with 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.



If the foot is seen from behind the heel it is typical to be able to see the two outer toes, and seeing more means the forefoot is turned outwards. The physiotherapist will measure the angle made by the lower leg in relation to that of the heel, an angle which is increased as the heel bone turns outwards, a position known as valgus. On going up on tiptoe a normal foot performs a slight inward deviation of the heel as the large calf muscles power up.

Jonathan Blood Smyth, editor of the Physiotherapy Site, writes articles about Physiotherapist, back pain, orthopaedic conditions, neck pain, injury management and physiotherapists in Liverpool. Jonathan is a superintendant physiotherapist at an NHS hospital in the South-West of the UK.