Foot & Ankle

Posterior Tibial Tendon Dysfunction / Adult Acquired Flatfoot

Adult acquired flatfoot deformity (AAFD) is one of the most progressive and potentially disabling conditions of the foot and ankle. It develops when the posterior tibial tendon (PTT) — the foot's primary dynamic arch stabilizer — deteriorates and fails, allowing the medial longitudinal arch to collapse and the hindfoot to drift into valgus. Left untreated, the deformity progresses from a supple, correctable flatfoot to a rigid, arthritic deformity requiring major reconstructive surgery or joint fusion. Early recognition and appropriate staged treatment can halt this progression and restore function. Maryland Orthopedic Specialists offers comprehensive evaluation and the full spectrum of surgical reconstruction for all stages of this condition.

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What is posterior tibial tendon dysfunction / adult acquired flatfoot?

Posterior tibial tendon dysfunction occurs when the tendon supporting the arch of the foot weakens or tears, causing the arch to gradually collapse, known as adult-acquired flatfoot. Symptoms include pain and swelling along the inner ankle, a flattening foot, and difficulty standing on the toes.

The posterior tibial tendon runs behind the medial malleolus and inserts on the navicular and plantar midfoot. When functioning normally, it inverts the hindfoot during the single-leg stance phase of walking and maintains the arch. When the tendon degenerates — from repetitive overload, age, obesity, hypertension, seronegative arthropathy, or prior corticosteroid injection — the static ligamentous stabilizers (spring ligament, deltoid ligament, plantar fascia) become progressively overloaded and fail as well.

Johnson-Strom Classification (Modified)

Stage I: Tendon tendinopathy without deformity. The tendon is intact but painful and swollen; the arch is maintained; single-leg heel rise is painful but possible.

Stage II: Tendon rupture or severe attenuation with flexible (correctable) deformity. The hindfoot is in valgus, the arch is collapsed, and the forefoot abducts ("too many toes sign"). Single-leg heel rise is weak or impossible. The deformity corrects passively.

Stage III: Rigid flatfoot deformity with fixed hindfoot valgus and forefoot abduction. The deformity cannot be passively corrected. Subtalar and/or transverse tarsal arthritis is present.

Stage IV: Stage III changes with additional ankle valgus due to deltoid ligament insufficiency and early ankle arthritis.

Key Clinical Tests

"Too many toes" sign: Viewed from behind, more than the lateral 1–2 toes are visible on the affected side due to forefoot abduction and hindfoot valgus. Sensitive for Stage II+ disease.
Single-leg heel rise test: The patient rises on one leg; a normal response is the heel inverting into varus as the PTT locks the subtalar joint. Inability to perform the test or failure to invert indicates significant PTT dysfunction. Comparison to the contralateral side is essential.
Silfverskiöld test: Assesses Achilles/gastrocnemius contracture (equinus), which is commonly associated with AAFD and may require surgical lengthening.

Treatment options

Treatment is matched to how far the condition has progressed — most patients with early disease do well with orthotics and physical therapy.

Stage I — Non-Operative

Anti-inflammatory medication and a period in a walking boot calm the tendon inflammation, followed by custom arch-supporting orthotics and a targeted physical therapy program. Most Stage I patients stabilize and remain comfortable without surgery.

Stage II — Bracing and Surgery

A rigid ankle brace (AFO) supports the arch when the tendon can no longer do so on its own. For patients who want a more durable solution, surgical reconstruction combines a tendon transfer with corrective bone cuts to restore the arch and relieve the overloaded tendon.

Surgical Procedure

Posterior Tibial Tendon Reconstruction (Flatfoot Correction)

Staged surgical reconstruction of adult flatfoot deformity combining flexor digitorum longus tendon transfer with calcaneal osteotomy, lateral column lengthening, or subtalar fusion — staged to match the degree of deformity and residual flexibility.

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Frequently Asked Questions

Can a flatfoot "become" AAFD, or are they different?

Congenital or lifelong flatfoot is usually asymptomatic and does not represent PTT dysfunction. AAFD is acquired — patients describe their arch "falling" over time, often with a history of medial ankle pain. The distinction matters for treatment.

Will orthotics cure my flatfoot?

Orthotics cannot restore tendon or ligament integrity. They support the foot's remaining structure and relieve symptoms but are not curative. They are excellent long-term solutions for patients managing early-stage disease or those who are not surgical candidates.

Can AAFD lead to ankle arthritis?

Yes. Chronic hindfoot valgus shifts the mechanical axis of the limb medially, concentrating load on the medial ankle compartment, eventually leading to Stage IV disease with deltoid insufficiency and tibiotalar arthritis.

Do I need the whole fusion or is there a less invasive option?

Rigid (Stage III) deformity requires arthrodesis. Flexible (Stage II) deformity can be managed with the tendon transfer and osteotomy combination described above, preserving hindfoot motion. Stage selection is critical — an operation designed for Stage II will fail in a Stage III foot.

How long is recovery after flatfoot reconstruction surgery?

Recovery after surgical correction of adult acquired flatfoot deformity is one of the longer orthopaedic rehabilitation journeys — typically nine to twelve months to full function. The first six weeks require non-weight-bearing to allow bone cuts, osteotomies, and tendon transfers to heal. Gradual weight-bearing in a boot follows, with formal physical therapy beginning around eight to twelve weeks. Your MOS foot and ankle surgeon will monitor bone healing with serial X-rays and guide your progression; swelling in the foot and ankle can persist for up to a year, but most patients achieve significant, lasting improvement in alignment, pain, and function.

Meet the specialists

Gary Feldman, DPM, FACFAS

Podiatry (Foot & Ankle Surgery)

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Related conditions

Achilles Tendinopathy Ankle Osteoarthritis Ankle Sprains / Chronic Lateral Ankle Instability

Medically reviewed by Gary Feldman, DPM, FACFAS, DPM, FACFAS

Last reviewed May 1, 2026

References

Johnson KA, Strom DE. Tibialis posterior tendon dysfunction. Clinical Orthopaedics and Related Research. 1989;(239):196–206. doi:10.1097/00003086-198902000-00022
Myerson MS. Adult acquired flatfoot deformity: treatment of dysfunction of the posterior tibial tendon. Journal of Bone and Joint Surgery (American). 1996;78(5):780–792. doi:10.2106/00004623-199605000-00024
Guyton GP, Jeng C, Krieger LE, Mann RA. Flexor digitorum longus transfer and medial displacement calcaneal osteotomy for posterior tibial tendon dysfunction. Foot & Ankle International. 2001;22(8):627–632. doi:10.1177/107110070102200803
Ellis SJ, Williams BR, Wagshul AD, Pavlov H, Deland JT. Deltoid ligament reconstruction with peroneus longus autograft in flatfoot deformity. Foot & Ankle International. 2010;31(9):781–789. doi:10.3113/FAI.2010.0781
OrthoInfo — AAOS. Posterior Tibial Tendon Dysfunction. Available at: https://orthoinfo.aaos.org/en/diseases--conditions/posterior-tibial-tendon-dysfunction