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

Tarsal coalition is an abnormal bony, cartilaginous, or fibrous bridge between two or more tarsal bones that restricts subtalar and midtarsal joint motion. The condition is a common and frequently overlooked cause of rigid flatfoot and recurrent ankle sprains in adolescents and young adults, with symptoms often emerging during the second decade of life as the coalition ossifies.

Types and Prevalence

Calcaneonavicular coalition (between the calcaneus and navicular bones) and talocalcaneal coalition (between the talus and calcaneus, most commonly at the middle facet) account for over 90% of tarsal coalitions. Incidence is approximately 1% of the population, with 50–60% bilateral. Tarsal coalition has a hereditary component with autosomal dominant transmission identified in some family clusters.

Clinical Presentation

Adolescents with tarsal coalition typically present with activity-related lateral hindfoot pain, rigid or semi-rigid flatfoot deformity, and limited subtalar joint motion on clinical examination. A characteristic “peroneal spastic flatfoot” — with peroneal muscle spasm resisting subtalar inversion — is pathognomonic of advanced talocalcaneal coalition. Recurrent ankle sprains from limited hindfoot mobility compensation are a common secondary complaint. Adults may present with premature subtalar and ankle arthritis as a consequence of long-standing coalition.

Imaging Diagnosis

Weight-bearing foot and ankle radiographs provide initial screening — the “anteater sign” (elongated anterior process of calcaneus) on lateral X-ray suggests calcaneonavicular coalition; the “C-sign” suggests talocalcaneal coalition. CT scan is the gold standard for defining coalition morphology, size, and articular involvement. MRI evaluates fibrocartilaginous coalitions, adjacent bone marrow edema, and associated peritalar arthritis — critical for surgical planning.

Conservative Management

Initial treatment for symptomatic coalition includes activity modification, custom orthotics with medial arch support, and short-term immobilization (walking boot or cast) for 4–6 weeks. Corticosteroid injection into the coalition or adjacent joints may provide temporary relief. Conservative management succeeds in 25–40% of patients but is less effective for osseous coalitions and those with significant articular damage.

Surgical Treatment: Resection vs. Fusion

Coalition resection (excision of the coalition with interposition of fat or muscle to prevent re-ossification) is the preferred procedure for patients with limited articular damage and adequate remaining joint space. Calcaneonavicular coalition resection has excellent outcomes (80–90% good to excellent results) when performed before secondary osteoarthritic changes develop. Talocalcaneal coalition resection has more variable results influenced by coalition size — coalitions involving more than 50% of the middle facet surface area are associated with higher failure rates and consideration of primary subtalar fusion. Subtalar or triple arthrodesis is appropriate for coalitions with secondary arthritis, large coalition size, or failed resection.

Tarsal Coalition Evaluation at Balance Foot & Ankle

Dr. Biernacki at Balance Foot & Ankle evaluates suspected tarsal coalition with on-site weight-bearing radiographs and CT coordination at the first visit. Both conservative management and surgical referral for coalition resection are available for adolescent and adult patients. Call (810) 206-1402 for a same-week evaluation.

Tarsal Coalition Treatment in Michigan

Tarsal coalition — abnormal bone or cartilage bridges between foot bones — causes rigid flat feet, recurrent ankle sprains, and foot pain in adolescents and young adults. Our podiatrists provide accurate diagnosis and both conservative and surgical treatment.

Get Expert Tarsal Coalition Care → | Book Your Appointment | Call (810) 206-1402

Clinical References

1. Crim JR, Kjeldsberg KM. “Radiographic Diagnosis of Tarsal Coalition.” American Journal of Roentgenology. 2004;182(2):323-328.
2. Docquier PL, et al. “Tarsal Coalition in Paediatric Patients: A Review.” Orthopaedics & Traumatology: Surgery & Research. 2019;105(1S):S123-S131.
3. Mosca VS. “Subtalar Coalition in Pediatrics.” Foot and Ankle Clinics. 2015;20(4):625-644.

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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.