Adult Acquired Flatfoot

Adult acquired flatfoot deformity (AAFD or AAF) is a progressive, symptomatic deformity resulting from gradual stretch of the posterior tibial tendon as well as other ligaments supporting the arch of the foot. AAFD develops after skeletal maturity,  [1] May also be referred to as posterior tibial tendon dysfunction (PTTD), although due to the complexity of the disorder AAFD is more appropriate. Significant ligamentous rupture occurs as the deformity progresses. Involved ligaments include the spring ligament, the superficial deltoid ligament, the plantar fascia, and the long and short plantar ligaments. Unilateral AAFD is more common than bilateral AAFD.

Stages of AAFD/PTTD [2]Edit

Stage 1Edit

  • Symptoms are minor and may go unnoticed
  • Pain dominates, rather than deformity
  • Minor swelling may be visible along the course of the tendon

Stage 2Edit

  • Tendinopathy, pain and swelling along the course of the tendon
  • Visible decrease in arch height
  • Abduction of the forefoot on rearfoot
  • Subluxed tali and navicular joints
  • Deformation at this point is still flexible

Stage 3Edit

  • Considerable deformity and weakness
  • Significant pain
  • Arthritic changes in the tarsal joints
  • Deformation at this point is rigid

Stage 4Edit

  • Severe flatfoot
  • Complete valgus collapse of the talus
  • Possible necrotic ulcerations along the mid-arch collapse
  • Substantial pain caused by tendon failure and destructive changes in joints

Causes & Risk Factors [3]Edit

  • Overuse of the posterior tibial tendon
  • Surgery or trauma to the posterior tibial tendon or medial aspect of the ankle
  • Neurologic weakness
  • Rheumatoid arthritis
  • Hypertension
  • Obesity
  • Diabetes

Incidence [4]Edit

  • It is estimated that approximately 1 in 20 adults have some form of flatfoot
  • AAFD is more common in people above the age of 40
  • Average AAFD onset at age 60
  • AAFD is more common in females than in males, although the reason why is unknown

Symptoms [5]Edit

  • Pain along the path of the posterior tibial tendon
  • Pain may shift laterally as the deformity progresses

Signs & Tests [6]Edit

  • Redness or swelling along the course of the tendon
  • Visibly subluxed or malaligned joints
  • Inability to pass the single heel rise test is evidence of AAFD
  • X-ray images may be useful in determining the extent of the deformity

Treatment [7]Edit

Stage 1Edit

The goal in stage 1 is to halt the progression of the tendinopathy through conservative methods in order to prevent tendon rupture. Treatments at this stage include, in order:

  1. A short leg walking boot or short leg walking cast for 6-8 weeks
  2. Full length semi-rigid foot orthosis
  3. Physical therapy to stretch the Achilles tendon and strengthen the posterior tibial tendon

Stage 2Edit

By stage 2, a flexible deformity has developed and more control is required to prevent further pronation and deformity. Surgery is controversial at this stage, as conservative treatment is usually successful. Treatment options are as follows:

  • A rigid UCBL orthosis
  • An articulated AFO

Stage 3 & 4Edit

The goal at stage 3 and 4 is the same; to accommodate the deformity, prevent or slow further deformity, and in some cases to improve walking ability by transferring load away from the collapsed midfoot and hindfoot. Treatment options are as follows:

  • Solid ankle AFO
  • Limited motion double upright AFO
  • Patellar tendon bearing AFO

Other Treatment Options[8]Edit

  • Weight loss
  • Exercises aimed at strengthening the posterior tibial tendon
  • Surgical options include lateral column lengthening, medial column stabilization, and arthrodesis


Prognosis is dependent upon which stage the disorder has progressed to before treatment was begun. Starting in stage 1 or 2, the deformity may stabilize or regress to the point of only requiring a semi-rigid or rigid foot orthosis. Starting in stage 3 or 4, the deformity will likely have progressed to the point where orthotic intervention will only ever accommodate the deformity and slow further deformation.