Tarsal coalition is a congenital abnormality in which two or more tarsal bones in the midfoot or hindfoot are fused by an abnormal bridge of bone, cartilage, or fibrous tissue. The fusion restricts normal subtalar or midtarsal joint motion and produces a characteristic rigid flatfoot deformity with reduced or absent hindfoot flexibility. Tarsal coalition is one of the most commonly missed diagnoses in adolescent foot pain — presenting as “flat feet,” “ankle sprains,” or nonspecific activity-related foot and ankle pain that fails to improve with standard treatment. At Balance Foot & Ankle in Howell and Bloomfield Hills, MI, Dr. Tom Biernacki, DPM evaluates and manages tarsal coalition in children, adolescents, and adults who have reached adulthood without diagnosis.

What Is Tarsal Coalition?

Tarsal coalitions are abnormal connections between tarsal bones that develop during fetal limb bud formation and become symptomatic as the fibrous or cartilaginous bridge ossifies during adolescence. The two most common coalition types are calcaneonavicular coalition (between the anterior calcaneus and the navicular — approximately 45% of cases) and talocalcaneal coalition (between the talus and calcaneus at the middle facet of the subtalar joint — approximately 45% of cases). Less common coalitions involve the calcaneocuboid, cubonavicular, and talonavicular joints. Coalitions may be unilateral or bilateral; bilateral coalitions are present in approximately 50% of patients and may have different clinical presentations on each side depending on the extent of ossification and joint motion restriction.

When Does Tarsal Coalition Become Symptomatic?

Tarsal coalitions are typically asymptomatic in early childhood when the bridge consists of flexible fibrous or cartilaginous tissue that allows some joint motion. Symptoms emerge between ages 8–16 years as the coalition progressively ossifies — calcaneonavicular coalitions typically present at ages 8–12, talocalcaneal coalitions at ages 12–16. The ossification converts a flexible bridge into a rigid bar that restricts normal subtalar or midtarsal motion, producing peroneal muscle spasm (a reflex protective response to the restricted motion), flatfoot deformity, and activity-related ankle and foot pain. The timing corresponds closely to increased athletic demands of middle and high school sports, which is why tarsal coalition is frequently mistakenly attributed to athletic overuse or “growing pains.”

Symptoms — Recognizing Tarsal Coalition

The characteristic symptoms of tarsal coalition are: a rigid, non-correctable flatfoot deformity (the heel does not swing into varus when the patient rises on tiptoe — the Jack test is negative); peroneal muscle spasm producing a valgus hindfoot posture that the patient cannot voluntarily correct; activity-related pain in the sinus tarsi, midfoot, or along the peroneal tendons; and stiffness after rest that improves with walking but worsens with increased activity. In our clinic, the single most specific clinical finding is the absence of subtalar motion — normally, the heel should rock inward and outward by 20–30° with passive manipulation; in coalition, this motion is severely reduced or absent. Recurrent ankle sprains in an adolescent with a rigid flatfoot should always raise suspicion for tarsal coalition because the restricted hindfoot motion increases the likelihood of ankle sprain from minor stumbles that a normal hindfoot would absorb.

Diagnosis — X-Ray, CT, and MRI

Calcaneonavicular coalition is often visible on standard oblique foot X-ray as an elongated bony bridge or “anteater sign” (the anterior calcaneal process extending toward and potentially touching the navicular). Talocalcaneal coalition is more difficult to identify on plain X-rays but produces characteristic secondary changes: talar beaking (a dorsal talar spur), broadening of the lateral talar process, and middle facet narrowing or fusion on the Harris axial view. CT scan is the definitive imaging modality for coalition classification, assessment of the extent of ossification, and surgical planning — it provides precise three-dimensional visualization of the coalition anatomy. MRI is most useful for fibrous coalitions that are not visible on CT, demonstrating abnormal signal intensity at the coalition site and characterizing the surrounding soft tissue edema and joint effusion.

Conservative Treatment

Conservative management is appropriate for symptomatic coalitions in the acute phase and for milder cases without significant peroneal spasm or secondary deformity. The goals are to reduce pain, improve function, and delay surgery until skeletal maturity if possible. Immobilization in a short-leg cast or CAM walker for 4–6 weeks resolves acute peroneal spasm and allows inflammation to settle. Custom functional orthotics with a medial arch post and deep heel cup support the flatfoot deformity and reduce the abnormal stress at the coalition site during activities. Activity modification — reducing impact activities and avoiding the specific sports or movements that provoke spasm — is essential during the conservative management phase. Physical therapy focused on gastrocnemius-soleus flexibility and tibialis posterior strengthening supports the residual foot architecture. Conservative management reduces symptoms in approximately 30–40% of symptomatic tarsal coalition patients — complete resolution is uncommon because the structural abnormality persists.

Surgical Treatment — Coalition Resection and Reconstruction

Surgical intervention is indicated when conservative management fails to provide adequate symptom control, when secondary degenerative arthritis has not yet developed, and when the coalition anatomy is amenable to resection. Coalition resection — surgically excising the abnormal bone or cartilaginous bridge — is the primary procedure for calcaneonavicular and smaller talocalcaneal coalitions. After resection, the gap is filled with the extensor digitorum brevis muscle (for calcaneonavicular coalitions) or fat graft (for talocalcaneal coalitions) to prevent recalcification. Successful resection restores subtalar motion and resolves peroneal spasm in approximately 70–80% of carefully selected patients. For patients with large talocalcaneal coalitions, extensive secondary deformity, or significant arthritic change in adjacent joints, isolated resection has poor results — subtalar fusion (arthrodesis) combined with corrective osteotomies to address the flatfoot deformity is the more appropriate surgical plan.

Red Flags — When to Seek Evaluation for an Adolescent’s Flat Feet

Seek podiatric evaluation for a child or adolescent with flat feet if: the flatfoot is rigid — the arch does not appear when the child rises on tiptoe or sits with feet off the ground; one foot is flatter than the other (asymmetric flat feet are a red flag for coalition or posterior tibial tendon dysfunction); the child has recurring ankle sprains or ankle pain; there is visible peroneal muscle bulging on the outer lower leg at rest; activity-related foot pain is limiting participation in sports or PE; or a teenager reports “ankle stiffness” that has gradually worsened over months to years. Flexible pediatric flatfoot requires no treatment; rigid flatfoot requires investigation.

Tarsal Coalition Treatment at Balance Foot & Ankle — Michigan

Dr. Tom Biernacki, DPM evaluates tarsal coalition with in-office weight-bearing X-ray, Harris axial views, CT coordination for coalition classification, and full biomechanical assessment of secondary deformity. Conservative management including custom orthotics and activity modification, and surgical resection or reconstruction for appropriate candidates, are available. Appointments at our Howell office (4330 E Grand River Ave, Howell MI 48843) and Bloomfield Hills office (43494 Woodward Ave #208, Bloomfield Hills MI 48302). Call (810) 206-1402 or

book online.

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.