Acquired Adult Flatfoot Deformity

What is Adult Acquired Flatfoot Deformity (also known as Posterior Tibial Tendon Dysfunction (PTTD))

Adult acquired flatfoot deformity occurs when the posterior tibial tendon degenerates or tears. This tendon is one of the main support mechanisms of the arch and as a result, with its dysfunction the arch of the foot is no longer supported which can result in a flat foot deformity.

Tibialis posterior tendonPeople with this problem generally are unable to stand on one leg and lift the heel off the ground and if the condition has been present for a while they commonly present with a flat foot. Typically pain is also present along the course of the tendon,  just behind or below the ankle joint (see yellow area)

Tibialis posterior tendon dysfunction

Ultrasound examination at The Foot and Ankle Centre can assist in diagnosing this problem. Below shows the position of the probe and the findings in posterior tibial tendon degeneration.

Probe position Note the fluid surrounding the tendon Fibres of the tendon are discontinuous
Ultrasound of tibialis posterior tendon Ultrasound of tibialis posterior tendon
Ultrasound of tibialis posterior tendon Ultrasound of tibialis posterior tendon


What Causes of Adult Acquired Flat Foot Deformity

  • Trauma – acute trauma to the tendon can result in its degeneration this is commonly seen in inversion ankle sprains
  • Certain Connective tissue disorders
  • Biomechanical abnormalities- The main cause of Posterior TIbial Tendon Dysfunction is having an overly flat foot.  This is because the position of the foot changes the demand from certain muscle groups.
    Neutral Foot In a neutral foot  the muscles on the inside of the foot (invertors) work just as hard as the muscles on the outside of the foot (evertors).
    Flat FootMuscle balance flat foot In a flat foot the muscles on the inside of the foot (invertors) work a lot harder to try and correct the position of the foot  – overtime this can result the degeneration of the tibialis posterior tendon.

Stages of Adult acquired Flat Foot Deformity

  • Stage 1 – Posterior tibial tendon intact and acutely inflammed, no deformity, mild -moderate swelling
  • Stage 2 – Posterior tibial tendon dysfunctional, acquired flat foot but passively correctable.
  • Stage 3 – Degenerative changes in the subtalar joint and the deformity is fixed
  • Stage 4 – Degenerative changes in the ankle joint


Complications of Adult Acquired Flat Foot Deformity


Treatment of Adult Acquired Flat Foot Deformity

Treatment of adult acquired flat foot deformity is difficult due to the fact that there is relatively poor blood supply to the area of the tendon just behind the ankle joint, which means it seldom repairs.

Treatment therefore depends on the stage and degree of the deformity.

In the acute stage of the deformity the aim is to rest the tendon and minimise swelling. When the tendon has settled the aim of treatment is to prevent the traumatic lengthening of the tendon, this is achieved by minimising the activity of the invertor muscles and tendons

  • Orthotics with a rearfoot post –There are a number of different orthotic designs available for flat feet. Most orthotic designs are simply arch supports.
    These are not ideal for the flat foot, often only irritating the arch of the foot.
  • Footwear modification
  • Lace up ankle brace
  • Arizona brace
  • Ankle Foot Orthotic
  • Surgery



The Ankle, Foot and Orthotic Centre’s Northcote Podiatrists can help you with all lower limb complaints, including Ankle Pain. Make an appointment to get your foot and ankle pain under control.

Expert Podiatrists for the treatment of Adult Acquired Flat Foot Deformity servicing the areas of Northcote, Thornbury, Fitzroy, North Fitzroy, Carlton, North Carlton, Alphington, Fairfield, Brunswick, Coburg and Preston