Adult Acquired Flatfoot

Adult acquired flatfoot deformity (AAFD) is more common in middle aged adults, particularly females with an elevated BMI and has a reported prevalence in the UK between 3%-10%. Equivalent to 2.04 and 6.79 million people.

AAFD is a rather complex condition that has been previously described to have four stages known as the Johnson and Strom classification system (Abousayed et al., 2016). The pathogenesis was historically described as Posterior Tibialis Tendon Dysfunction. The main function of this muscle is to provide dynamic stabilisation of the inner arch of the foot. This initial dysfunction can lead to a cascade of worsening pathological events. Therefore, early diagnosis may be important in delaying or preventing worsening symptoms associated with this condition.

There are a number of structures involved in AAFD with the two main structures being the Calcaneonavicular ligament (left) and the Tibialis Posterior tendon (Pictured above). Both of which provide stability to the inner arch of your foot.

The Tibialis Posterior tendon originates at the posterior & medial boarder of the Tibia (shin bone), Fibular (matchstick bone) and interosseous membrane (connective tissue between the bones). This muscle has a long tendon which descends down the inner aspect of your leg, inserting on a small bone on the inside of the foot called the Navicular.

The Calcaneonavicular ligament also known as the ‘spring ligament’ forms a stabilising attachment between the calcaneus (heel bone) and the navicular, helping to maintain the inner arch.

Often pain will start along your instep of the foot with pain developing behind the inner ankle bone and up the inner aspect of your leg. You may have difficulty walking with a generalised ache which may exacerbate throughout the day. A defining symptom is often an inability or difficulty to heel rise (up on tip toes) because your Tibialis Posterior tendon has a reduced capacity to perform this effectively. As symptoms and the condition deteriorate, inner ankle pain may be followed by  pain in the outside of the ankle also – resulting from biomechanical changes.

• Flat footedness – most people who develop the condition already have flat feet. With overuse or continuous loading which reinforces poor biomechanics, a change occurs where the arch begins to flatten excessively, with pain and swelling developing.

• Inadequate support from footwear may occasionally be a contributing factor.

• Trauma or injury – occasionally this condition may be due to fracture, sprain or direct blow to the tendon.

• Age – the risk of developing Tibialis Posterior Tendon Dysfunction increases with age and research has suggested that middle aged women are more commonly affected.

• Other possible contributing factors– being overweight, diabetes and inflammatory arthritis.

If identified early enough, AAFD can generally be managed conservatively with specific advice and a personalised and progressive strengthening programme which your specialist Physiotherapist can design to increase the strength of the soft tissues involved. Additionally, custom made ankle foot orthoses (AFO’s) from a podiatrist are often provided to support the inner foot arch to reduce your symptoms, complementing the above outlined Physiotherapy input.

Later stages of AAFD may require surgical intervention to provide joint fusions and correct deformity. This typically involves a combination of removing bone to correct the angle of the calcaneus, and repairing the Tibialis Posterior tendon. In the most severe cases, internal fixation techniques may be utilised which involves the placement of screws and plates to improve structural integrity (Volcano, Deland & Ellis 2013).

Abousayed, M. M., Tartaglione, J. P., Rosenbaum, A. J., & Dipreta, J. A. (2016). Classifications in brief: Johnson and Strom classification of adult-acquired flatfoot deformity.

Alvarez, R. G., Marini, A., Schmitt, C., & Saltzman, C. L. (2006). Stage I and II posterior tibial tendon dysfunction treated by a structured nonoperative management protocol: an orthosis and exercise program. Foot & ankle international, 27(1), 2-8.

Vulcano, E., Deland, J. T., & Ellis, S. J. (2013). Approach and treatment of the adult acquired flatfoot deformity. Current reviews in musculoskeletal medicine, 6(4), 294-303.