Board-certified foot & ankle surgeon · 20+ years treating adult-acquired flatfoot & PTTD · Howell & Bloomfield Hills, MI
Last reviewed: May 2026
Quick answer
Posterior tibial tendonitis (PTT) is inflammation of the tendon running behind the inner ankle bone. If left untreated it progresses to posterior tibial tendon dysfunction (PTTD) and adult-acquired flatfoot. PTT/PTTD is staged 1-4: stages 1-2 respond to custom orthotics + medial heel post + eccentric strengthening in 70-80% of patients. Stage 3-4 (rigid deformity, established arthritis) requires surgical reconstruction. The diagnostic clue: pain along the inner ankle, inability to do single-leg heel rise on the affected side, and progressive arch collapse over months. Don’t wait — the conservative care window closes once the deformity becomes rigid.
What posterior tibial tendonitis is
The posterior tibial tendon is the main dynamic stabilizer of your arch. It runs from your calf muscle, BEHIND the inner ankle bone, and inserts on multiple bones of the arch. When you walk, it actively pulls up on the arch and inverts the foot.
When this tendon becomes inflamed (posterior tibial tendonitis), painful, or starts to fail, the arch can no longer maintain its shape. The result is a cascade:
- Stage 1 (inflammation): Pain along inner ankle, arch still intact
- Stage 2 (flexible flatfoot): Arch collapses but is still passively correctable
- Stage 3 (rigid flatfoot): Arch deformity is permanent, secondary arthritis
- Stage 4 (ankle valgus): Ankle joint itself starts to tilt — the worst presentation
This is one of the most under-recognized progressive orthopedic conditions — patients often delay treatment for years until they have permanent arch collapse.
Recognizing it early
- Pain along the inner ankle (the bony bump on the inside)
- Swelling along the tendon path (from below the inner ankle to the arch)
- Difficulty pushing off the affected foot
- “Too many toes” sign — when viewed from behind, more toes visible on the outside of the foot than expected (sign of foot abduction)
- Inability to perform single-leg heel rise on the affected side — the most diagnostic test
- Worse with prolonged standing, walking, going down stairs
Stand on one foot. Try to rise up on the ball of that foot. If you can’t do this on one side but can on the other — you likely have PTTD. This 30-second test is more diagnostic than many imaging studies. If positive, get evaluated within 2-4 weeks. The longer it goes untreated, the more likely you’ll progress to rigid deformity requiring surgery.
Diagnosis
- Single-leg heel rise test — primary functional test
- Direct palpation along the tendon course
- Foot architecture assessment — arch height, hindfoot valgus
- Weight-bearing X-rays — assess for bony arch collapse, talonavicular subluxation
- MRI — gold standard for tendon integrity, partial tears, peritendinous edema, and bone marrow edema. Required before surgical planning.
- Diagnostic ultrasound — useful office-based imaging for tendon thickening/tendinopathy
Treatment by stage
Stage 1 — Tenosynovitis without deformity
- 2-4 weeks CAM walker boot for inflammation control
- NSAIDs short course (oral + topical diclofenac)
- Custom orthotic with medial heel post (3-5mm), deep heel cup, medial flange
- 12-week structured eccentric exercise protocol — resisted inversion (TheraBand), single-leg heel rise progression
- Calf stretching (tight Achilles drives compensatory pronation)
- Conservative success rate: 80-90% at this stage
Stage 2 — Flexible flatfoot deformity
- Arizona AFO brace 3-6 months (more support than orthotic alone)
- Custom orthotic with 5-7mm medial heel post + UCBL-style deep cup
- Eccentric strengthening continues for 6-12 months
- Activity modification — avoid prolonged standing, running on uneven terrain
- Conservative success rate: 50-70%. If failing at 6 months, surgical reconstruction is considered.
Stage 3 — Rigid flatfoot
- Conservative care is palliative — bracing/orthotics can manage pain but cannot reverse the deformity
- Surgical reconstruction is the definitive treatment:
- Medializing calcaneal osteotomy + FDL tendon transfer
- Possible lateral column lengthening (Evans osteotomy)
- Possible Cotton osteotomy for forefoot supination
- Subtalar fusion if arthritic
- Recovery: 6 weeks NWB + 6 weeks WB in boot + 3 months rehab
Stage 4 — Ankle valgus
- Surgical management with deltoid ligament reconstruction + hindfoot procedures
- Triple arthrodesis if extensive arthritis
- Recovery typically 6+ months
When to see a podiatrist
- Inner ankle pain persisting >1 week without improvement
- Inability to do single-leg heel rise on the affected side
- Visible arch collapse compared to opposite foot
- Progressive worsening over weeks/months
- Risk factors: obesity, diabetes, prior ankle trauma, age >40
Catch PTTD early — before the arch collapse is permanent
Custom orthotic + eccentric protocol catches 80-90% of Stage 1 PTTD. The window closes once it becomes rigid.
Bottom line
PTTD is the most common cause of adult-acquired flatfoot. Stage 1-2 has excellent outcomes with conservative care; Stage 3-4 needs surgery. The window matters. If you suspect it — get the single-leg heel rise test, then a podiatry visit. The cost of delay is measured in years of progressive deformity and the difference between a custom orthotic and a 6-month surgical recovery.
— Dr. Tom Biernacki, DPM, FACFAS
Dr. Tom Biernacki, DPM is a board-certified foot & ankle surgeon (ABFAS & ABPM) 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 made him one of the most-followed foot & ankle educators on YouTube.