Tarsal Coalition: Abnormal Bone Fusion Causing Flat Foot and Ankle Pain in Children and Adults

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

What Is Tarsal Coalition?

Tarsal coalition is an abnormal connection — a bridge of bone, cartilage, or fibrous tissue — between two or more of the tarsal bones in the hindfoot and midfoot. This abnormal bridge restricts or eliminates the normal motion between the affected bones, causing a rigid or semi-rigid flatfoot deformity, recurrent muscle spasms, and progressive pain that typically emerges during adolescence as the bridge ossifies (becomes bone).

Tarsal coalition is present from birth — it develops during embryonic limb development from failure of the mesenchymal tissue between adjacent tarsal bones to properly differentiate and separate. The condition is bilateral (affecting both feet) in approximately 50 to 60 percent of cases. Prevalence in the general population is estimated at 1 to 2 percent, though many cases are never identified because they remain asymptomatic.

At Balance Foot & Ankle, our podiatrists are experienced in diagnosing tarsal coalition in both adolescents and adults who may have gone years with unexplained ankle pain or rigid flat feet. Accurate diagnosis is the foundation of effective treatment planning.

Types of Tarsal Coalition

Calcaneonavicular Coalition

The most common type, accounting for approximately 45 percent of tarsal coalitions. An abnormal bridge connects the anterior calcaneus to the navicular bone on the medial side of the midfoot. Calcaneonavicular coalition typically becomes symptomatic between ages 8 and 12 as the coalition ossifies. It is best visualized on the 45-degree oblique foot X-ray and CT scan.

Talocalcaneal Coalition

The second most common type, comprising approximately 45 percent of cases. The coalition occurs at the middle facet of the subtalar joint — where the talus and calcaneus normally have an independent cartilaginous joint surface. Talocalcaneal coalition typically becomes symptomatic between ages 12 and 16. Plain X-rays may show the C-sign or talar beaking, but CT scan is typically required for definitive diagnosis as this coalition is in a complex three-dimensional location.

Other Coalition Types

Talonavicular, calcaneocuboid, and cuboidonavicular coalitions are rare, comprising the remaining 10 percent. Multiple simultaneous coalitions affecting several tarsal bones occur in some patients.

Symptoms of Tarsal Coalition

The hallmark presentation is a rigid or semi-rigid flat foot in an adolescent with activity-related hindfoot and ankle pain. Unlike flexible flatfoot — which is usually painless and corrects spontaneously with heel rise — tarsal coalition produces a flat foot that does not correct with tip-toe standing or non-weight bearing. This rigidity is a critical examination finding.

Peroneal spastic flatfoot is a classic presentation: recurrent, painful spasms of the peroneal muscles on the outer ankle that occur in response to attempted subtalar motion against the coalition. The spasm is the foot protecting the coalition site from excessive stress. Adolescents with recurrent peroneal muscle spasms and flat feet should be evaluated for tarsal coalition until proven otherwise.

Pain is typically located over the sinus tarsi (the depression in front of the lateral malleolus), beneath the medial ankle, or diffusely throughout the hindfoot. Symptoms characteristically worsen with activity on uneven terrain and improve with rest. Patients report the foot feeling locked and unable to accommodate to irregular surfaces — because it literally cannot.

Recurrent ankle sprains are common in tarsal coalition patients because the restricted hindfoot motion prevents normal terrain adaptation, causing the ankle to absorb all accommodative stress. An adolescent with multiple ankle sprains and flat feet warrants evaluation for coalition.

Diagnosis

Physical examination documents the degree of subtalar motion restriction, the presence or absence of peroneal spasm, heel alignment, and the correction or rigidity of the flat foot deformity. Standing foot X-rays including 45-degree oblique views are the initial imaging study. CT scan is the gold standard for tarsal coalition, providing three-dimensional assessment of the coalition type, extent, and associated arthritic changes. MRI is valuable for cartilaginous or fibrous coalitions that may not be visible on CT.

Conservative Treatment

Initial treatment for symptomatic tarsal coalition is always conservative. Activity restriction during acute symptom flares combined with immobilization in a CAM boot or short leg cast allows inflammation to subside. Custom orthotics designed to support the foot and redistribute loads through the rigid coalition area provide symptomatic relief for many patients with partial motion preservation.

Physical therapy focuses on reducing peroneal muscle spasm, maintaining ankle range of motion, and strengthening the intrinsic foot muscles and peroneals for dynamic stabilization. Anti-inflammatory medications reduce acute pain. Corticosteroid injection into the coalition site provides temporary relief.

Conservative care is appropriate as the primary treatment for mild to moderate symptoms, for patients with significant arthritic changes at the coalition site where surgery would be limited to fusion rather than resection, and for patients who decline surgery. Some patients manage their condition conservatively for years with orthotics and activity modification.

Surgical Treatment

Resection (Bar Excision)

When coalition resection is feasible — requiring a coalition that involves less than 50 percent of the joint surface and minimal adjacent arthritis — surgical removal of the coalition restores motion and relieves pain. The abnormal bridge is excised, and fat or muscle tissue is interposed to prevent re-fusion. Results are excellent in appropriately selected patients, with majority reporting good to excellent outcomes and return to full activity.

Resection is most appropriate in younger patients (under approximately 16 years) before progressive arthritic changes develop at the coalition site and surrounding joints.

Arthrodesis (Fusion)

When arthritic changes are advanced, when coalition resection is not feasible, or when resection has failed, arthrodesis of the affected joint complex is the appropriate surgical option. Subtalar fusion for talocalcaneal coalition eliminates the painful, arthritic joint motion. The functional loss is meaningful but well tolerated, particularly when the coalition has already substantially eliminated motion before surgery.

If you have an adolescent or young adult family member with flat feet, recurrent ankle sprains, or hindfoot pain, consider tarsal coalition evaluation at Balance Foot & Ankle. We serve patients of all ages throughout Southeast Michigan with comprehensive foot and ankle care.

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Tarsal Coalition Treatment at Balance Foot & Ankle

Tarsal coalition is a congenital condition where two or more foot bones are abnormally connected, causing stiffness and pain. Dr. Tom Biernacki at Balance Foot & Ankle provides expert diagnosis and both conservative and surgical treatment at our Howell and Bloomfield Hills offices.

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Clinical References

1. Cowell HR. “Tarsal coalition — review and update.” Instructional Course Lectures. 1982;31:264-271.
2. Mosier KM, Asher M. “Tarsal coalitions and peroneal spastic flat foot: a review.” Journal of Bone and Joint Surgery. 1984;66(7):976-984.
3. Kernbach KJ. “Tarsal coalitions: etiology, diagnosis, imaging, and stigmata.” Clinics in Podiatric Medicine and Surgery. 2010;27(1):105-117.

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