Medically Reviewed | Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle, Michigan
Quick Answer:
Quick Answer: Tarsal coalition is an abnormal bony or fibrous fusion between two tarsal bones — most commonly calcaneonavicular or talocalcaneal — causing rigid flatfoot, peroneal muscle spasm, and activity-limiting hindfoot pain. Dr. Biernacki provides accurate diagnosis with CT imaging and personalized surgical or conservative treatment.
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What Is Tarsal Coalition?
Tarsal coalition is a congenital fusion — bony (synostosis), cartilaginous (synchondrosis), or fibrous (syndesmosis) — between two or more of the tarsal bones of the hindfoot and midfoot. The most common types are calcaneonavicular coalition (CN coalition, ~50% of cases) and talocalcaneal coalition at the middle facet (~25% of cases). The abnormal connection prevents normal subtalar joint motion, resulting in a rigid flatfoot that cannot form a normal arch when standing on tiptoe.
Tarsal coalition is present at birth but typically becomes symptomatic during adolescence — ages 8–16 — as the fibrocartilaginous coalition ossifies into bone and restricts motion. Bilateral coalition is present in 50–60% of cases. The condition often runs in families, suggesting autosomal dominant inheritance with variable penetrance.
Symptoms and Clinical Presentation
The hallmark triad is: rigid flatfoot that does not correct on tiptoe standing, peroneal muscle spasm or tightness (historically called “peroneal spastic flatfoot”), and activity-related hindfoot or midfoot pain. Patients describe pain with sports, prolonged standing, and walking on uneven terrain. Ankle sprains occur with increased frequency due to restricted subtalar motion and altered proprioception.
Physical examination reveals a planovalgus (flat, everted) hindfoot that does not correct with heel rise — distinguishing coalition from flexible flatfoot. Subtalar joint motion is markedly restricted. Peroneal tendon tightness on passive inversion is characteristic. Neurological examination is normal.
Diagnosis: Imaging Is Essential
Plain radiographs provide initial clues — the “anteater sign” (elongated anterior calcaneal process) suggests CN coalition on lateral view, while the “C-sign” (continuous C-shaped outline of talus and sustentaculum tali) suggests talocalcaneal coalition. However, CT scan is the gold standard for definitive diagnosis, coalition type characterization, and surgical planning. MRI is preferred for fibrous coalitions that may not be visible on CT and for assessment of adjacent joint arthritic change.
Dr. Biernacki’s diagnostic protocol ensures complete characterization of coalition morphology, extent of arthritic change in adjacent joints, and presence of bilateral disease before treatment planning.
Conservative Treatment
Initial treatment aims to control pain and peroneal spasm with activity modification, anti-inflammatory medication, and custom orthotics. Rigid custom orthotics with medial arch support and heel valgus wedging can significantly reduce pain by optimizing the mechanical environment within the restricted joint. Corticosteroid injection into the coalition site or retrocalcaneal bursa provides temporary relief during acute flares.
Short-leg cast immobilization for 4–6 weeks is effective for acute symptom flares — particularly useful in younger adolescents during growth spurts when the coalition is ossifying. Many patients achieve adequate long-term symptom control with conservative care alone, particularly those with fibrous or cartilaginous (incompletely ossified) coalitions.
Surgical Treatment
Surgery is indicated when conservative care fails to provide adequate pain relief after 3–6 months. For patients without significant subtalar joint arthritis, coalition resection — surgical removal of the abnormal bony bridge — restores joint motion and is highly effective, particularly in younger patients with CN coalition. Interposition of fat graft or extensor digitorum brevis muscle prevents re-ossification of the resection site.
In patients with extensive coalition, significant subtalar arthritic changes, or failed previous resection, hindfoot arthrodesis (subtalar, double, or triple fusion) provides reliable pain relief at the cost of motion. Dr. Biernacki tailors the surgical approach to each patient’s coalition type, arthritic burden, and functional goals.
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Conservative management of tarsal coalition flatfoot
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✅ Pros / Benefits
- Coalition resection in adolescents has excellent outcomes with motion restoration
- Conservative care manages many cases to acceptable function
- CT imaging provides definitive characterization for surgical planning
❌ Cons / Risks
- Subtalar arthritic changes preclude resection — arthrodesis required
- Bilateral cases require staged surgical treatment
- Coalition recurrence after resection possible if interposition inadequate
Dr. Tom Biernacki’s Recommendation
Tarsal coalition is frequently misdiagnosed as simple flatfoot or recurrent ankle sprains for years before the correct diagnosis is made. When a young patient has a rigid flatfoot and keeps spraining their ankle, I always think about coalition. CT scan gives us the answer definitively, and resection in the right candidate genuinely gives them back their motion.
— Dr. Tom Biernacki, DPM | Board-Certified Podiatric Surgeon | Balance Foot & Ankle
Frequently Asked Questions
At what age is tarsal coalition diagnosed?
Most cases become symptomatic and are diagnosed between ages 8–16 as the coalition ossifies during skeletal development. Adult-onset symptoms do occur, particularly after trauma that stresses the previously compensated coalition.
What is the difference between flexible and rigid flatfoot?
Flexible flatfoot corrects (arch forms) when standing on tiptoe. Rigid flatfoot from tarsal coalition does NOT correct on tiptoe — the restricted subtalar joint prevents arch formation.
Is tarsal coalition surgery successful?
Coalition resection in appropriately selected patients (younger age, no significant arthritis, complete resection) has excellent success rates — over 85% good or excellent outcomes. The key is proper patient selection using CT imaging.
Will my child outgrow tarsal coalition?
The coalition itself does not resolve, but some children with fibrous or cartilaginous coalitions achieve adequate function with orthotics and activity modification. Persistent pain despite conservative care is an indication for surgical evaluation.
Does tarsal coalition cause ankle sprains?
Yes. Restricted subtalar motion alters hindfoot mechanics and proprioception, significantly increasing lateral ankle sprain frequency. Recurrent sprains in young patients warrant evaluation for underlying coalition.
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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.
- Diagnosis and Treatment of Plantar Fasciitis (PubMed / AAFP)
- Heel Pain (APMA)
- Hallux Valgus (Bunions): Evaluation and Management (PubMed)
- Bunions (Mayo Clinic)