A variety of foot problems can lead to adult acquired flatfoot deformity (AAFD), a condition that results in a fallen arch with the foot pointed outward.


Depending on the cause of the flatfoot, a patient may experience one or more of the different symptoms below:

  • Pain along the inside of the foot and ankle. This can be associated with swelling on the inside of the ankle along the posterior tibial tendon.
  • Pain that is worse with activity; especially running. Patients can have difficulty walking or even standing for long periods of time.
  • As the foot collapses, the patient can develop pain on the outside ankle bone (fibula). This is known as ankle impingement.

The causes of acquired flat foot syndrome can happen for several reasons.

  • Damage to the posterior tibial tendon (PTT) is the most common cause.
  • Arthritis – arthritis in the back(hindfoot) or the middle(midfoot) of the foot can cause the arch to collapse. This is worse in patients with inflammatory arthritis such as rheumatoid arthritis.
  • Ligament injuries – ligaments support the bones and prevent them from moving. Injury to the ligaments (like tears) can cause the foot to become flat. The most common ligament injury leading to a flat foot is a lisfranc injury.

The treatment of acquired flat foot syndrome is to treat the symptoms and limit the progression. Most patients will feel great improvement with orthotics or bracing and are able to function fully. If there is an underlying inflammatory condition, this will need to be addressed to limit the progression of pes planus. There is also a role for physiotherapy to strengthen the muscles and ligaments of the foot and ankle.