What Is Tarsal Coalition? Causes, Symptoms & Treatment

Tarsal coalition is a condition in which two or more bones in the back or middle of the foot are abnormally connected by bone, cartilage, or fibrous tissue, restricting the foot’s normal motion and frequently causing pain.¹ It develops before birth but often stays silent until adolescence, when the connecting bridge stiffens and the demands on the foot increase. Because the symptoms can look a lot like a stubborn ankle sprain or generic flat feet, many people go years without an accurate diagnosis.

How Tarsal Coalition Forms

During early fetal development, the bones of the foot start as a single block of tissue that gradually separates into individual bones with joints between them. Tarsal coalition happens when that separation process fails at one or more sites, leaving an abnormal bridge of tissue where a joint cleft should have formed.² The bridge can be made of bone (a complete, rigid fusion), cartilage, or fibrous connective tissue. Cartilaginous and fibrous bridges allow a small amount of motion and tend to be harder to spot on standard X-rays.

The condition is congenital, meaning it is present from birth even though symptoms usually appear much later. It has a genetic component: it runs in families and shows up bilaterally, affecting both feet, in roughly half of patients.³ Males are somewhat more commonly affected than females, though the reason for that skew is not well understood.

The Two Most Common Types

The foot has seven tarsal bones, and coalitions can theoretically form between any pair, but two combinations account for the vast majority of cases. Calcaneonavicular coalition connects the heel bone (calcaneus) to the navicular bone on the inner side of the midfoot. Talocalcaneal coalition bridges the talus (the bone that sits on top of the heel) to the calcaneus at the subtalar joint. Together, these two types make up the overwhelming majority of diagnosed coalitions.

Less common variants include talonavicular coalition, cuboid-navicular coalition, and calcaneocuboid coalition. In rare cases, a person can have more than one coalition in the same foot.¹ The type and location of the coalition matter for treatment decisions because they determine which motions are restricted and which surgical approaches are feasible.

When and Why Symptoms Appear

Most coalitions are present from birth but do not cause problems in early childhood because the bridge is still made of flexible cartilage. As a child grows, that cartilage gradually turns to bone, a process called ossification. Different coalition types ossify on different timelines: talonavicular coalitions begin to stiffen as early as age three to five, calcaneonavicular coalitions around eight to twelve, and talocalcaneal coalitions between twelve and sixteen. The progressive stiffening, combined with the increased physical demands of adolescence, is what typically triggers the onset of symptoms.

The classic presentation is a teenager who develops a deep, aching pain on the outer side or the back of the foot, worsened by activity and sometimes accompanied by an obviously flat arch. The pain is not caused by the bridge itself but by the biomechanical disturbance it creates: with part of the hindfoot or midfoot locked, the surrounding joints are forced to absorb stresses they were not designed for.⁴ That extra stress can cause muscle spasm in the peroneal tendons along the outside of the ankle, leading to what clinicians call “peroneal spastic flatfoot,” a rigid flat foot where the muscles clamp down and make the foot even stiffer.

Not everyone follows this textbook pattern, however. In one study of adult patients with tarsal coalition, the majority had a neutral heel alignment rather than obvious flatfoot, and peroneal spasm was only seen in a small minority.⁵ Some people have mild symptoms they attribute to normal foot fatigue. Others are entirely asymptomatic: one case report described a man with massive bilateral tarsal coalition, meaning nearly all the tarsal bones in both feet were fused, who had no symptoms at all until degenerative arthritis set in years later.⁶

How Common Is It, and Who Gets It

Prevalence estimates vary depending on how you look. A radiographic study of a healthy, asymptomatic population found tarsal coalitions in about 0.4% of adults.⁷ Older estimates, based on cadaver dissections and clinical series, have ranged somewhat higher, but even at the upper end the condition is not rare. The gap between the number of coalitions that exist and the number that cause symptoms is wide. Many coalitions are discovered incidentally during imaging for an unrelated problem and never require treatment.³

Getting the Right Diagnosis

One of the biggest challenges with tarsal coalition is that its symptoms mimic several other foot and ankle conditions. It has been specifically identified as one of the diagnoses commonly misread as a simple ankle sprain, especially in children and adolescents.⁸ A teenager with repeated “ankle sprains” that never fully resolve, or a flat foot that is unusually rigid and painful, should raise suspicion.

On physical exam, the key finding is reduced or absent subtalar motion. If you try to tilt the heel inward and outward while holding the ankle steady and there is almost no movement, that is a red flag. Standing on tiptoe normally restores the arch in a flexible flat foot; in a foot with a coalition, the arch often stays flat even on tiptoe because the subtalar joint cannot adjust.

X-Rays

Standard foot X-rays are usually the first imaging step and can catch many coalitions. An oblique view of the foot is particularly good at showing calcaneonavicular coalitions, which often appear as a bony bar or an abnormally elongated navicular bone reaching toward the heel. Talocalcaneal coalitions are trickier on plain film, but trained observers have achieved strong detection rates when looking for specific signs like an abnormally shaped sustentaculum tali or loss of the normal middle subtalar joint space.⁹ Another classic X-ray clue is “talar beaking,” a spur that forms on the top of the talus due to abnormal stress, though this is an indirect sign rather than proof of the coalition itself.

CT and MRI

When X-rays are inconclusive or a surgeon needs precise information before operating, cross-sectional imaging comes next. CT scans are excellent at showing the size and exact location of bony coalitions and are the traditional gold standard for surgical planning. However, CT can miss coalitions that are made of cartilage or fibrous tissue rather than bone. In one series of calcaneonavicular coalitions in children, CT missed four out of eleven cases, including both cartilaginous and fibrous forms.¹⁰

MRI fills that gap. It can distinguish between bony, cartilaginous, and fibrous bridges, and it picks up associated soft-tissue problems like inflammation around the coalition, bone marrow swelling, and cartilage damage in nearby joints.¹¹ That information matters because the type of tissue making up the coalition influences both the expected natural course and the surgical approach. In practice, many centers use CT for preoperative planning when a bony coalition is already confirmed by X-ray, and reserve MRI for cases where the coalition type is uncertain or when soft-tissue complications are suspected.

Conservative Treatment

Not all tarsal coalitions need surgery. If you have mild or moderate symptoms, non-surgical treatment is the usual first step and works well for a substantial number of people. A large review of non-operative outcomes found that pain relief was achieved in roughly half to two-thirds of trials across different conservative approaches, with no single method clearly outperforming the others.¹² That same review found that surgery was avoided in about two-thirds to three-quarters of patients regardless of which conservative method was used.

The main conservative options include activity modification, anti-inflammatory medication, supportive shoe inserts or custom orthotics, and short-term immobilization in a walking boot or cast. A walking boot for several weeks can calm down an acute flare, and there is case-level evidence of complete symptom resolution with this approach even in adults.¹³ Physical therapy focusing on ankle and foot flexibility, calf stretching, and strengthening of the muscles that support the arch is also commonly prescribed. The goal of all these measures is the same: reduce stress on the restricted joints and give the surrounding tissues time to settle down.

The practical question people want answered is whether conservative treatment is just delaying the inevitable. For a meaningful majority of patients, the answer appears to be no. Many do well enough with non-surgical management that they never need an operation. But if pain keeps coming back with activity, or if the foot is becoming progressively stiffer and flatter, those are signs that the conservative route has reached its limits.

Surgical Options

Surgery generally comes into play when conservative treatment has failed to control symptoms adequately. The approach depends on the type of coalition, how much of the joint surface it covers, the patient’s age, foot alignment, and whether degenerative changes have already set in.

Coalition Resection

For smaller coalitions without significant arthritis in the surrounding joints, the standard operation is resection: the surgeon removes the abnormal bridge of tissue to restore motion at the joint. To prevent the coalition from growing back, a spacer material is placed into the gap. Fat taken from the patient’s own body (usually from nearby tissue) is the most commonly used interposition material, but fibrin glue and bone wax are alternatives.¹⁴ A comparative study found that the recurrence rate after resection was low with either fat graft or fibrin glue, with no significant difference between the two methods.¹⁵

Resection outcomes are generally favorable. A long-term review of nearly a hundred resections found that patients returned to their desired activity level with significantly improved function scores, at an average of about four and a half months after surgery.¹⁶ In young athletes, the surgical plan typically also considers whether the foot alignment needs correction at the same time, since some patients with talocalcaneal coalition have a rigid flatfoot that will not self-correct just from removing the bar.

When Resection Is Not Enough

If the coalition covers more than roughly half of the subtalar joint surface, or if there is already arthritis in the affected joint, removing the bar alone is unlikely to help. In those cases, the preferred option is arthrodesis, a surgical fusion of the joint. This sounds counterintuitive since the problem is unwanted fusion, but the goal of arthrodesis is different: it fuses the joint in a corrected position that relieves pain and improves the overall alignment of the foot.¹⁷ Newer techniques allow this to be done arthroscopically through small incisions, which can speed recovery compared to traditional open surgery.

In patients who have both a coalition and a rigid flatfoot deformity, the coalition resection is often combined with flatfoot reconstruction procedures such as a calcaneal lengthening osteotomy, tendon transfers, or other realignment steps. The combination addresses both the stiffness and the malalignment in a single operation.¹⁴

Recovery After Surgery

The post-operative course varies by procedure. After a simple resection, most protocols involve a period of non-weight-bearing in a splint or cast for several weeks, followed by a transition into a walking boot and then gradual return to activity. In the large retrospective series mentioned earlier, the average time to return to full activity was about eighteen weeks, though there was wide variation depending on the size and type of coalition and whether additional procedures were performed.¹⁶ Physical therapy is standard after the initial healing period to rebuild ankle mobility and strength.

For arthrodesis, recovery is longer. The fused joint needs time for the bone to fully heal, and patients may be in a cast or boot for two to three months before beginning to bear weight normally. Long-term, a fused subtalar joint does limit the foot’s ability to adapt to uneven surfaces, but most patients find the trade-off acceptable because the pain and instability they experienced before surgery are gone.

Long-Term Complications If Left Untreated

Many asymptomatic coalitions never cause problems and never need treatment. But when a symptomatic coalition goes undiagnosed or untreated for years, it can lead to secondary changes in the foot. The abnormal stress distribution forces neighboring joints to compensate, and over time this can cause osteoarthritis in the subtalar joint, the ankle, or other tarsal joints. A bony spur on the top of the talus, called a talar beak, is one of the more recognizable secondary signs and develops because of chronic abnormal motion at the talonavicular joint.¹⁸ Once significant arthritis has developed, simple resection of the coalition becomes less effective, and joint fusion or more extensive reconstruction may be the only remaining surgical options.

This is one of the reasons accurate early diagnosis matters. In a teenager with vague foot pain, the difference between catching a tarsal coalition now and discovering it ten years later with arthritis can be the difference between a relatively straightforward resection and a more complex procedure with a longer recovery.

Tarsal Coalition in the Young Athlete

Sports-active adolescents are the population most commonly diagnosed with symptomatic tarsal coalition, and they also tend to be the most motivated to return to full activity as quickly as possible. The surgical decision-making in young athletes takes into account not just the coalition itself but also foot alignment and whether degenerative joint changes have started.¹⁹ A coalition caught early, before secondary arthritis develops, is much more amenable to a clean resection with good restoration of motion.

Parents sometimes worry that their child will never be able to play sports again. The evidence is reassuring on this point: most patients in the long-term resection series returned to their desired activity level. The four-and-a-half-month average return time means that an adolescent who has surgery early in an off-season can realistically be back on the field by the next season, though individual timelines vary. Rushing the recovery to meet a sports deadline, on the other hand, risks re-injury or coalition recurrence and is generally discouraged.

When an Adult Gets Diagnosed for the First Time

Although tarsal coalition is usually framed as a pediatric condition, a meaningful number of adults are diagnosed for the first time in their twenties, thirties, or later. Some had mild symptoms throughout adolescence that were never investigated. Others were genuinely asymptomatic until a change in activity level, weight gain, or an acute injury tipped the balance. Adult presentation tends to include more prominent degenerative changes in the surrounding joints compared with adolescents, which can complicate treatment.⁴

The good news is that the same conservative measures that work in teenagers, such as orthotics, activity modification, and boot immobilization, can also work in adults. Surgery is reserved for those who do not respond, just as in younger patients, though the threshold for arthrodesis rather than resection tends to be lower in adults because the joints have had more time to develop secondary arthritis. Adults should not assume that being diagnosed later means worse outcomes; many do well with appropriate treatment, and even some with very extensive coalitions remain functional for decades before needing intervention.⁶

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2
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3
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PubMed. Tarsal coalition in adults
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PubMed Central. Talocalcaneal Coalition Resection with Local Fat Grafting and Flatfoot Reconstruction
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PubMed. Fibrin Glue is a Viable Alternative to Fat Graft for Interposition After Tarsal Coalition Resection
16
PubMed Central. Tarsal coalition resections: a long-term retrospective analysis of 97 resections in 78 patients
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PubMed Central. Lateral Arthroscopic Subtalar Arthrodesis for Talocalcaneal Coalition: Surgical Technique
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PubMed Central. Symptomatic talar beak in talocalcaneal coalition
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PubMed Central. Tarsal Coalition: Surgical Management in the Young Athlete