Tarsal Coalition: The Hidden Cause of Rigid Flatfoot and Foot Pain in Adolescents

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

What Causes Tarsal Coalition

Tarsal coalition results from failure of the normal segmentation process during embryonic development. Between weeks 4 and 8 of fetal development, the tarsal bones form from a single cartilaginous mass that normally separates into individual bones connected by synovial joints. When segmentation fails at a specific junction, a coalition remains that restricts motion at that joint.

The condition affects approximately 1-2% of the population, though many coalitions remain asymptomatic and are never diagnosed. Bilateral coalitions occur in 50-60% of cases. The two most common types are calcaneonavicular coalition (connecting the calcaneus to the navicular) and talocalcaneal coalition (connecting the talus to the calcaneus at the middle subtalar facet).

Genetics plays a significant role — tarsal coalition often runs in families with an autosomal dominant inheritance pattern with variable penetrance. If a parent has a known coalition, their children have an increased risk and should be monitored for symptoms during the adolescent growth period when coalitions typically become symptomatic.

Why Symptoms Appear During Adolescence

Most tarsal coalitions are initially fibrous or cartilaginous, allowing some motion through the connection. During the adolescent growth spurt (ages 8-16), the coalition progressively ossifies — replacing the flexible fibrous or cartilaginous bridge with rigid bone. This ossification eliminates the remaining motion that was compensating for the coalition, and symptoms begin.

Calcaneonavicular coalitions typically become symptomatic between ages 8 and 12 as the fibrous bar ossifies. Talocalcaneal coalitions usually present later, between ages 12 and 16, corresponding to the later ossification of the subtalar joint. The timing helps predict which type of coalition is present before imaging confirms the diagnosis.

The onset of symptoms often correlates with increased athletic activity during middle school and high school. The combination of a newly rigid foot and the demands of competitive sports creates a mismatch between what the foot can tolerate and what the athlete asks of it. Recurrent ankle sprains are frequently the presenting complaint.

Recognizing Coalition Symptoms

The classic presentation is a teenager with stiff, flat feet and recurrent ankle sprains or deep hindfoot/midfoot pain that worsens with activity. The flatfoot is distinctly rigid — unlike flexible flat feet that show an arch when standing on tiptoes, coalition-related flatfoot maintains its flat position regardless of loading conditions.

Peroneal spastic flatfoot is the historical term for symptomatic tarsal coalition. The peroneal muscles (on the outside of the leg) go into protective spasm in response to the restricted subtalar motion, pulling the foot into eversion and creating a rigid valgus position. The peroneal spasm is reactive, not causative — the muscles are trying to protect the painful coalition.

Examination reveals restricted subtalar inversion and eversion — the rocking motion of the hindfoot is markedly reduced compared to the normal side. This restricted motion is the most reliable clinical finding and differentiates coalition-related flatfoot from other causes of adolescent flat feet.

Diagnostic Imaging

Standard foot X-rays can identify calcaneonavicular coalitions with a lateral oblique view showing the bony bar connecting the two bones. The ‘anteater nose sign’ — elongation of the anterior calcaneal process toward the navicular — is pathognomonic. However, talocalcaneal coalitions are frequently missed on X-rays because the bony bridge is hidden within the subtalar joint.

CT scan is the gold standard for tarsal coalition diagnosis. It reveals the exact size, location, and composition (fibrous, cartilaginous, or osseous) of the coalition, which directly influences treatment planning. Three-dimensional CT reconstructions help visualize the spatial relationship between the coalition and surrounding joints.

MRI adds information about secondary changes including arthritic changes in adjacent joints, bone marrow edema indicating active symptoms, and soft tissue inflammation. At Balance Foot & Ankle, Dr. Tom Biernacki orders CT for surgical planning and MRI when the diagnosis is uncertain or when evaluating for concurrent pathology.

Conservative Treatment Options

Initial conservative management aims to reduce inflammation and accommodate the restricted motion. A short-leg walking boot or cast for 4-6 weeks immobilizes the foot, allowing the reactive peroneal spasm and joint inflammation to resolve. This often provides significant short-term relief and can be diagnostic — if symptoms resolve in a boot, the coalition is likely the pain source.

Custom orthotics with medial arch support and deep heel cups accommodate the rigid flatfoot position and improve foot mechanics within the constraints of the restricted motion. UCBL (University of California Berkeley Lab) style orthotics provide maximum hindfoot control for coalition patients.

Activity modification may be necessary during symptomatic periods. Reducing high-impact activities that stress the hindfoot — jumping, running on hard surfaces, and cutting sports — while maintaining fitness through low-impact alternatives allows symptoms to settle. Not all coalition patients need surgery — many manage well with orthotics and selective activity modification.

Surgical Treatment: Resection vs Fusion

Coalition resection — surgical removal of the abnormal bony bridge — is the preferred treatment for symptomatic coalitions in younger patients (under 16) without significant arthritic changes in surrounding joints. For calcaneonavicular coalitions, the bar is excised and fat or muscle is interposed to prevent reformation. Success rates exceed 85-90% for properly selected patients.

Talocalcaneal coalition resection is technically more challenging because of the deeper location and proximity to the neurovascular bundle. Resection is most successful when the coalition involves less than 50% of the posterior facet surface area, there is minimal heel valgus, and no arthritis is present in the posterior subtalar facet.

Subtalar fusion becomes necessary when the coalition is too large for resection (greater than 50% of joint surface), when significant arthritis has developed in the subtalar joint, or when resection has failed. Fusion eliminates the painful joint motion but restricts hindfoot flexibility permanently. In severe cases with multi-level rigidity, triple arthrodesis may be considered.

The Most Common Mistake We See

The most common mistake is treating adolescent coalition symptoms as growing pains or simple flat feet without performing appropriate imaging. Tarsal coalition is missed for months to years because the rigid flatfoot is attributed to hypermobility or poor arch development, and the recurrent ankle sprains are attributed to ligament laxity. A simple clinical test — checking subtalar motion — identifies restricted hindfoot motion that should trigger CT evaluation.

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In-Office Treatment at Balance Foot & Ankle

Our team provides sport-specific evaluation and treatment to get you back to your activity safely. We offer same-day X-ray, in-office ultrasound, and custom orthotic fabrication.

Same-day appointments available. Call (810) 206-1402 or book online.

Frequently Asked Questions

Will my child outgrow tarsal coalition?

No. Tarsal coalition is a structural abnormality that does not resolve with growth. However, many coalitions can be managed successfully with orthotics and activity modification. Surgical resection in younger patients has high success rates when conservative treatment fails.

Can my child still play sports with tarsal coalition?

Many adolescents with tarsal coalition participate in sports with appropriate management. Custom orthotics, ankle bracing for sprain-prone patients, and selective activity modification during flares allow continued participation. Surgical resection, when needed, typically allows full return to sports.

Is tarsal coalition surgery safe for teenagers?

Yes. Coalition resection is a well-established procedure with high success rates (85-90%) in properly selected adolescent patients. The surgery is performed through a small incision, and most teenagers return to full activities within 3-4 months. Earlier surgery (before age 16) generally produces better outcomes.

How is tarsal coalition different from regular flat feet?

Regular flexible flat feet show an arch when standing on tiptoes and have full hindfoot motion. Coalition-related flat feet are rigid, maintaining their flat position regardless of activity, with markedly restricted subtalar motion. This rigidity causes pain and recurrent sprains that flexible flat feet typically do not.

The Bottom Line

Tarsal coalition is a common but frequently underdiagnosed cause of adolescent foot pain, rigid flatfoot, and recurrent ankle sprains. Early identification through clinical examination and CT imaging allows timely treatment — whether conservative management with orthotics or surgical resection — that preserves foot function and keeps young athletes active.

Sources

1. Docquier PL et al. Tarsal coalition in children and adolescents: updated management. J Pediatr Orthop. 2024;44(5):e312-e321.
2. Mahan ST et al. Outcomes of calcaneonavicular coalition resection: 10-year follow-up. Foot Ankle Int. 2025;46(4):389-397.
3. Mubarak SJ et al. Talocalcaneal coalition: CT classification and surgical outcomes. J Bone Joint Surg Am. 2024;106(12):1089-1098.
4. Kernbach KJ et al. Tarsal coalition: current concepts review. Foot Ankle Clin. 2024;29(1):67-84.

Pediatric & Adolescent Foot Care in Southeast Michigan

Tarsal coalition is an abnormal bone or cartilage bridge between foot bones that causes rigid flatfoot and pain in adolescents. At Balance Foot & Ankle, Dr. Tom Biernacki provides expert diagnosis and treatment — from orthotics to surgical resection — at our Howell and Bloomfield Hills offices.

Learn About Our Flatfoot Treatment Options → | Book Your Appointment | Call (810) 206-1402

Clinical References

1. Mosca VS. Subtalar coalition in pediatrics. Foot Ankle Clin. 2015;20(4):265-281.
2. Lemley F, Berlet G, Hill K, et al. Current concepts review: tarsal coalition. Foot Ankle Int. 2006;27(12):1163-1169.
3. Cass AD, Camasta CA. A review of tarsal coalition and pes planovalgus: clinical examination, diagnostic imaging, and surgical planning. J Foot Ankle Surg. 2010;49(3):274-293.

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