Adult-Acquired Flatfoot: Posterior Tibial Tendon Dysfunction Stages and Treatment

Medically reviewed by Dr. Tom Biernacki, DPM — Board-Certified Podiatric Surgeon — Balance Foot & Ankle, Howell & Bloomfield Hills, MI. Last updated April 2026.

Adult-acquired flatfoot deformity (AAFD) — progressive collapse of the medial longitudinal arch in skeletally mature patients — is the most common cause of acquired flatfoot in adults and is synonymous with posterior tibial tendon dysfunction (PTTD) in the majority of cases. The condition follows a predictable clinical staging progression, with treatment options precisely tailored to each stage.

Pathomechanics of PTTD-Driven Flatfoot

The posterior tibial tendon is the primary dynamic stabilizer of the medial longitudinal arch, controlling subtalar joint supination during midstance and resupinating the foot for efficient toe-off. PTTD produces failure of this dynamic stabilizer through a combination of tendon degeneration and attenuation, allowing progressive subtalar joint valgus rotation, calcaneal eversion, and forefoot abduction. The spring ligament complex (superomedial calcaneonavicular ligament) — the primary static stabilizer of the talonavicular joint — elongates in parallel, permitting navicular plantarflexion and the characteristic midfoot sag of AAFD.

Johnson and Strom Classification of PTTD

Stage I PTTD involves tenosynovitis of the posterior tibial tendon without significant deformity — characterized by medial ankle pain, mild swelling, and intact single-leg heel rise test. Stage II involves elongation or partial tearing of the posterior tibial tendon with flexible flatfoot deformity — the single-leg heel rise is weak or absent, forefoot abduction is visible (“too many toes” sign), and the deformity is manually correctable. Stage IIA involves flexible deformity with the hindfoot reducible past neutral; Stage IIB involves a fixed forefoot abduction component. Stage III involves fixed (rigid) hindfoot valgus deformity with secondary subtalar and peritalar arthritic changes. Stage IV adds deltoid ligament attenuation with valgus talar tilt within the ankle mortise.

Stage-Specific Treatment

Stage I is managed with immobilization (walking boot, 4–6 weeks), custom orthotic arch support, and anti-inflammatory therapy following the acute phase. Stage II requires more aggressive orthotic management with a custom UCBL (University of California Biomechanics Laboratory) style orthosis providing full hindfoot control, and surgical reconstruction for failures — medializing calcaneal osteotomy, FDL tendon transfer, and spring ligament repair constituting the standard Stage II reconstruction. Stage III PTTD with fixed deformity and subtalar arthritis is managed surgically with subtalar or triple arthrodesis. Stage IV adds deltoid reconstruction or ankle arthrodesis to address tibiotalar malalignment.

PTTD Evaluation at Balance Foot & Ankle

Dr. Biernacki at Balance Foot & Ankle evaluates adult-acquired flatfoot with weight-bearing radiographs and clinical staging at the first visit. Custom UCBL orthotics, conservative Stage I management, and surgical reconstruction planning for Stage II–IV PTTD are all available. Call (810) 206-1402 for a same-week evaluation of new or worsening flatfoot.

When to See a Podiatrist

Many foot conditions can be managed conservatively at home, but some require professional evaluation. See a podiatrist promptly if you experience:

• Pain that persists for more than 2 weeks despite rest
• Swelling, redness, or warmth that isn’t improving
• Numbness, tingling, or burning in the feet
• A wound or sore that is not healing within 2 weeks
• Any foot concern if you have diabetes or poor circulation
• Nail changes that suggest fungal infection or other problems

At Balance Foot & Ankle, our three board-certified podiatrists — Dr. Tom Biernacki, Dr. Carl Jay, and Dr. Daria Gutkin — provide comprehensive foot and ankle care at our Howell and Bloomfield Township offices. Most insurance plans are accepted.

Your Board-Certified Podiatrists

Dr. Tom Biernacki, DPM

Board-Certified · FACFAS

Dr. Carl Jay, DPM

Board-Certified Podiatrist

Dr. Daria Gutkin, DPM

Podiatrist

Dr. Tom Biernacki, DPM

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Dr. Tom Biernacki, DPM is a double board-certified podiatrist and foot & ankle surgeon at Balance Foot & Ankle Specialists in Southeast Michigan. With over a decade of clinical experience, he specializes in heel pain, bunions, diabetic foot care, sports injuries, and minimally invasive surgery. Dr. Biernacki is a member of the APMA and ACFAS, and his patient education content on MichiganFootDoctors.com and YouTube has reached over one million views.