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) — also called posterior tibial tendon dysfunction (PTTD) or pes planovalgus — represents the progressive collapse of the medial longitudinal arch in adulthood, most commonly from failure of the posterior tibial tendon. Unlike flexible flatfoot present since childhood, AAFD develops in adults who previously had a normal or near-normal arch. It produces a characteristic constellation: arch collapse, hindfoot valgus (heel turning outward), forefoot abduction (“too many toes” sign), and progressive loss of pushoff strength. Understanding the clinical stages guides treatment decisions from early conservative management through complex reconstruction.

Causes and Risk Factors

The posterior tibial tendon (PTT) is the primary dynamic supporter of the medial arch — when it fails, no other structure compensates effectively. PTT dysfunction begins as tendinopathy (degenerative changes within the tendon), progresses through partial and complete tears, and eventually leads to ligamentous failure (spring ligament, deltoid) and rigid bony deformity. Risk factors include obesity (increased loading on the medial arch), hypertension, diabetes, corticosteroid use, and female sex (connective tissue laxity). The typical patient is a woman between 40–70 years old with gradual onset of medial ankle pain and arch flattening.

Johnson-Strom Staging (Updated)

Stage I: Tendinopathy Without Deformity

The PTT is painful and swollen but functional. The arch is preserved. Single-heel-rise test is normal. Conservative management with custom orthotics (UCBL or medial arch support), physical therapy (PTT strengthening), and anti-inflammatory treatment is the appropriate approach. Stage I responds well to conservative care.

Stage II: Flexible Flatfoot Deformity

The PTT is insufficient — the arch has collapsed and the hindfoot has entered valgus — but the deformity remains flexible (correctable passively). The single-heel-rise test is abnormal (patient cannot complete a single-leg heel rise or rises in a flat position). Conservative management includes rigid or semi-rigid orthotics with medial heel wedge and extended medial flange, functional brace (Arizona-type), and physical therapy. When conservative care fails, Stage II is treated surgically with soft tissue procedures (PTT repair or reconstruction, FDL tendon transfer) combined with bony procedures to restore arch alignment (medializing calcaneal osteotomy, lateral column lengthening, or both).

Stage III: Rigid Flatfoot Deformity

The flatfoot deformity has become rigid — the hindfoot valgus is fixed and cannot be corrected passively. Secondary arthritic changes in the subtalar and talonavicular joints are common. Surgical correction requires subtalar and/or talonavicular fusion to correct the rigid deformity, combined with medial column procedures as needed.

Stage IV: Valgus Tilt of the Ankle

In the most advanced stage, the deltoid ligament fails from chronic valgus loading, producing a valgus tilt of the ankle mortise itself. Stage IV deformity requires tibiotalar and subtalar fusion (tibiotalocalcaneal arthrodesis) or total ankle replacement combined with hindfoot correction.

Early Treatment Is Critical

The primary message about AAFD is that early treatment prevents progression. Stage I treated appropriately rarely progresses to Stage II; Stage II treated aggressively often avoids Stage III surgery. Conversely, untreated or undertreated early-stage disease predictably advances through stages. Any adult with new onset of medial ankle pain and arch change should be evaluated promptly — not observed for months without intervention.

Adult Acquired Flatfoot Treatment in Michigan

Adult acquired flatfoot from posterior tibial tendon dysfunction progressively collapses your arch and shifts your heel outward. Our podiatrists stage the condition accurately and offer targeted treatments — from custom orthotics and bracing to reconstructive surgery — to halt progression and restore foot function.

Learn About Flatfoot Treatment in Howell | Book Your Appointment | Call (810) 206-1402

Clinical References

1. Myerson MS. Adult acquired flatfoot deformity: treatment of dysfunction of the posterior tibial tendon. Instructional Course Lectures. 1997;46:393-405.
2. Bluman EM, et al. Posterior tibial tendon rupture: a refined classification system. Foot and Ankle Clinics. 2007;12(2):233-249.
3. Arangio GA, et al. Subtalar pronation — relationship to the medial longitudinal arch loading in the normal foot. Foot & Ankle International. 2004;25(4):200-205.

Dr. Tom Biernacki, DPM

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.