Tarsal Coalition: Symptoms, Diagnosis & Treatment | Podiatrist 2026

If your teenager has a ‘flat foot that won’t respond to orthotics’ and complains of ankle stiffness and pain after sports, tarsal coalition may be the diagnosis everyone has been missing. This congenital condition — present from birth but often not symptomatic until adolescence — is underdiagnosed because it requires specific imaging to identify. At Balance Foot & Ankle, we see tarsal coalition regularly and can determine whether the coalition is causing significant dysfunction warranting surgery.

What Is Tarsal Coalition?

The tarsal bones are the seven bones in the back and middle of the foot: calcaneus, talus, navicular, cuboid, and three cuneiforms. During embryonic development, these bones differentiate from a common mesenchymal mass. Tarsal coalition occurs when this differentiation fails in the joint space between two bones, leaving an abnormal connection that restricts normal subtalar and midtarsal motion.

Coalitions are classified by the tissue type of the bridge:

• Synostosis (osseous): Complete bony fusion — rigid, painful, appears on X-ray
• Synchondrosis (cartilaginous): Cartilage bridge — partially restricts motion, visible on CT/MRI
• Syndesmosis (fibrous): Fibrous tissue — least restrictive, often asymptomatic, MRI best for diagnosis

The Two Most Common Types

Calcaneonavicular (CN) Coalition

The most common type (45–60% of coalitions), connecting the anterior process of the calcaneus to the lateral aspect of the navicular. Best seen on the oblique foot X-ray and CT. Often presents as an ‘anteater sign’ on lateral X-ray (elongation of the anterior calcaneal process toward the navicular). Less likely to cause subtalar rigidity than TC coalition; more amenable to resection with good outcomes.

Talocalcaneal (TC) Coalition

The second most common type (40–50%), connecting the talus to the calcaneus at the middle facet of the subtalar joint. Best seen on CT. On lateral X-ray shows the ‘C sign’ — a continuous C-shaped arc formed by the fused middle facet talar dome and sustentaculum tali. Causes more rigid subtalar restriction than CN coalition; surgical resection outcomes are less predictable, especially when extensive.

Symptoms of Tarsal Coalition

Tarsal coalition is usually asymptomatic in childhood. Symptoms typically emerge in adolescence (ages 8–16) when the cartilaginous coalition begins ossifying and stiffening:

• Rigid flatfoot: The subtalar joint cannot evert and invert normally — the foot remains flat in both standing and toe-raise
• Midfoot or rearfoot pain: Aching or sharp pain over the sinus tarsi, medial arch, or below the lateral malleolus
• Peroneal spastic flatfoot: Classic presentation — the peroneal muscles spasm reflexively to guard the painful coalition, producing involuntary foot eversion
• Activity-related pain: Pain worsens with running, cutting, and uneven terrain; improves with rest
• Recurrent ankle sprains: Loss of subtalar motion impairs proprioception and balance, increasing inversion sprain risk
• Limited toe-raise: Inability to achieve full arch reconstitution on single-leg heel rise

Diagnosis

• Standing foot X-rays (3 views): Oblique view best for CN coalition; lateral for C-sign and anteater sign. May miss cartilaginous/fibrous coalitions.
• CT scan: Gold standard for coalition anatomy — defines the size, location, degree of ossification, and arthritic changes in adjacent joints. Essential for surgical planning.
• MRI: Best for fibrous and cartilaginous coalitions that are invisible on CT. Also evaluates surrounding soft tissue and bone edema.
• Clinical examination: Reduced or absent subtalar inversion/eversion, rigid flatfoot, peroneal muscle spasm on forced inversion

Subtalar joint range of motion is formally measured. < 50% of normal motion on the affected side compared to the contralateral foot suggests clinically significant restriction.

Tarsal Coalition Treatment

Conservative Treatment

Conservative treatment is the first approach for all symptomatic coalitions and is successful in 30–40% of patients:

• Activity modification: Reduce high-impact sports during symptomatic flare-ups; transition to swimming or cycling
• Custom orthotics (UCBL design): A rigid University of California Berkeley Lab (UCBL) orthosis or similar rearfoot-controlling device; reduces stress on the coalition and adjacent joints
• Short leg walking cast: 4–6 weeks of cast immobilization for acute painful episodes — reduces inflammation around the coalition
• NSAIDs: Naproxen or ibuprofen for inflammatory pain management
• Physical therapy: Peroneal stretching, intrinsic strengthening, proprioception training

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Surgical Treatment

Surgery is indicated when conservative treatment fails after 3–6 months, when the coalition is causing significant functional limitation, and when there are no significant arthritic changes in the adjacent joints:

• Coalition resection (excision): The coalition is surgically excised and the space filled with fat graft (interposition arthroplasty) to prevent re-ossification. Best results for CN coalitions and smaller TC coalitions (< 50% facet involvement). In adolescents, success rates of 70–90% are reported.
• Subtalar arthrodesis (fusion): When resection is not feasible (large TC coalition, extensive arthritis), fusing the subtalar joint eliminates motion through the arthritic segment. Highly reliable for pain relief; accepts the loss of what little subtalar motion remained.
• Triple arthrodesis: Fusion of the subtalar, talonavicular, and calcaneocuboid joints for severe rigid flatfoot with pan-tarsal arthritis — reserved for advanced cases

Frequently Asked Questions

At what age is tarsal coalition diagnosed?

Most patients are diagnosed between ages 8–16 when the coalition begins ossifying and symptoms emerge. However, fibrous coalitions may remain asymptomatic into adulthood and be found incidentally on imaging for another complaint. Bilateral coalitions are common — if one is found, the other foot should also be imaged.

Can tarsal coalition be treated without surgery?

Yes — 30–40% of patients achieve adequate pain control with conservative measures including custom orthotics, activity modification, and occasional cast immobilization. Surgery is only indicated when conservative treatment has genuinely failed and quality of life or athletic function is significantly impaired.

How successful is tarsal coalition surgery?

Calcaneonavicular coalition resection produces good or excellent results in 70–90% of adolescents when performed before significant arthritis develops. Talocalcaneal coalition resection results are less predictable (60–70% good outcomes) and depend heavily on the size of the coalition. Subtalar fusion for failed resection or advanced arthritis reliably eliminates pain.

Is tarsal coalition hereditary?

Yes — it is inherited as an autosomal dominant trait with variable expressivity. If you have a tarsal coalition, there is a meaningful chance your children carry the same genetic predisposition, though they may not develop symptoms. Bilateral involvement occurs in 50–60% of cases.

Can adults develop tarsal coalition?

Tarsal coalition is congenital — present from birth. Adults who are newly ‘diagnosed’ most commonly have a coalition that was always present but asymptomatic until an injury, weight gain, or increased activity level provoked symptoms. The coalition itself does not develop in adulthood.

Sources

• Mosier KM, Asher M. Tarsal coalitions and peroneal spastic flatfoot: a review. J Bone Joint Surg Am. 1984;66(7):976-984.
• Cowell HR, Elener V. Rigid painful flatfoot secondary to tarsal coalition. Clin Orthop Relat Res. 1983;(177):54-60.
• Westberry DE, Davids JR, Oros W. Surgical management of symptomatic talocalcaneal coalitions by resection of the sustentaculum tali. J Pediatr Orthop. 2003;23(4):493-497.
• Luhmann SJ, Schoenecker PL. Symptomatic talocalcaneal coalition resection: indications and results. J Pediatr Orthop. 1998;18(6):748-754.

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.