Adult Acquired Flatfoot Deformity
Overview
Adult acquired flatfoot deformity (AAFD) is a condition in which the arch of the foot gradually collapses after the foot has fully developed.
The problem most often affects one foot, though it can involve both.
It typically develops slowly, causing pain, swelling, and changes in foot shape that can interfere with walking and activity.


Etiology (Causes)
The most common cause is posterior tibial tendon dysfunction (PTTD)—damage or degeneration of the tendon that supports the arch.
Other contributors include:
  • Tendon rupture or chronic degeneration (posterior tibial, spring ligament, deltoid ligament)
  • Arthritis (rheumatoid, osteoarthritis, or post-traumatic)
  • Previous foot or ankle trauma
  • Obesity or high body weight
  • Diabetes or neuropathy
  • Steroid exposure or inflammatory conditions
Risk increases with age, female sex, and activities that stress the inside of the foot and ankle


Stages & Symptoms
AAFD is often staged to guide treatment:
  • Stage I: Tendon inflammation or mild degeneration, arch still present
  • Stage II: Progressive flattening, flexible deformity, hindfoot valgus
  • Stage III: Rigid flatfoot with arthritis
  • Stage IV: Involvement of the ankle joint

Typical symptoms include:
  • Pain and swelling along the inside of the ankle
  • Gradual flattening of the arch
  • Outward rolling of the heel
  • Difficulty standing on tiptoe
  • Pain on the outer ankle or midfoot as deformity progresses


Diagnosis
Diagnosis is based on history, physical examination, and imaging:
  • Physical exam: “Too many toes” sign, inability to perform a single-heel raise
  • X-rays: Evaluate alignment, arthritis, or collapse
  • MRI or ultrasound: Assess tendon quality and ligament damage


Treatment Options
Treatment depends on the stage of disease and severity of symptoms.
Non-Operative
  • Activity modification and rest
  • Immobilization with a walking boot or brace during acute inflammation
  • Custom orthotics or ankle-foot orthoses (AFOs) to support the arch
  • Physical therapy to strengthen supporting muscles and improve flexibility
  • Weight management and anti-inflammatory medications
Early and consistent non-surgical care can control symptoms and slow progression, especially in Stage I–II disease

Surgical
Surgery is considered when non-operative care fails or deformity is advanced.
Procedures may include:
  • Tendon transfer or repair (e.g., flexor digitorum longus transfer)
  • Calcaneal osteotomy (heel bone realignment)
  • Spring ligament or deltoid reconstruction
  • Arthrodesis (fusion) for rigid or arthritic joints
  • Ankle replacement or fusion in Stage IV disease
Surgical planning is individualized based on stage, flexibility, and patient health.


Expectations & Recovery
  • Non-surgical care: Symptom relief often within weeks; orthotic use may be lifelong to prevent progression.
  • Surgery: Recovery typically requires 6–12 weeks of non-weight-bearing followed by progressive weight-bearing and rehabilitation.
    Full recovery can take 6–12 months, with most patients experiencing pain relief and improved function.
Prognosis: Early detection and treatment greatly improve outcomes.
Advanced untreated cases can lead to chronic pain, arthritis, and significant loss of function.


References
  1. Bluman EM, Title CI, Myerson MS. Posterior tibial tendon rupture: diagnosis and treatment. J Am Acad Orthop Surg. 2007;15(7):376-385. PubMed
  2. Johnson KA, Strom DE. Tibialis posterior tendon dysfunction. Clin Orthop Relat Res. 1989;(239):196-206. PubMed
  3. Haddad SL, et al. Adult acquired flatfoot deformity. J Bone Joint Surg Am. 2011;93(17):1675-1692. PubMed
  4. Kulwicki KJ, et al. Nonoperative and operative management of posterior tibial tendon dysfunction: a systematic review. Foot Ankle Clin. 2021;26(2):221-246. PubMed
  5. National Institute of Arthritis and Musculoskeletal and Skin Diseases. Flatfoot in Adults. NIAMS
 
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