Calcaneonavicular Coalition Guide 2026 | DPM

Feature	Calcaneonavicular Coalition	Talocalcaneal Coalition
Frequency	~45% of tarsal coalitions	~50% of tarsal coalitions
Location	Anterior calcaneus → navicular	Middle subtalar facet (sustentaculum)
Classic X-ray sign	Anteater sign (oblique view)	C-sign, talar beaking (lateral view)
Best plain film view	Oblique foot view	Harris axial (heel) view
Pain location	Lateral foot / sinus tarsi	Medial hindfoot / sustentaculum
Surgical success rate	80–90% with resection	70–80% with resection (if <50% facet)
Interposition material	Extensor digitorum brevis (EDB)	Fat graft or FHL tendon

Recovery Phase	Timeline	Activity Level
Post-op immobilization	0–3 weeks	NWB cast; foot elevated
Protected weight-bearing	3–6 weeks	Walking boot; partial WB
PT / mobilization	6–12 weeks	Subtalar ROM; peroneal strengthening
Return to sport (low impact)	3–4 months	Cycling, swimming, walking
Return to sport (full)	4–5 months	Running, cutting sports; with custom orthotics

Quick answer: A calcaneonavicular coalition is an abnormal bridge of bone or cartilage connecting the heel bone (calcaneus) to the navicular. It is present from childhood, usually becomes painful in adolescence, and limits hindfoot motion — the classic cause of a rigid, painful flatfoot. Many cases settle with immobilization and orthotics; persistent ones respond well to surgical resection. We treat this regularly at our Howell and Bloomfield Township practices. Call (810) 206-1402.

What Is Tarsal Coalition?

Tarsal coalition is a congenital abnormal union between two or more tarsal bones. The two most common types are calcaneonavicular coalition (CN coalition, accounting for ~53% of cases) and talocalcaneal coalition (~37%). The bridge can be bony (synostosis), cartilaginous (synchondrosis), or fibrous (syndesmosis).

Symptoms of Calcaneonavicular Coalition

Symptoms typically appear in adolescence (ages 8–12 for CN coalition) when the coalition ossifies and limits motion. Classic presentation: painful rigid flatfoot, peroneal muscle spasm (peroneal spastic flatfoot), limited subtalar motion, and pain with prolonged walking or sports. Ankles sprain frequently due to limited hindfoot motion. Some coalitions are asymptomatic and found incidentally.

Diagnosis

Lateral X-ray shows the “anteater sign” — elongation of the anterior calcaneal process bridging toward the navicular. Oblique foot X-ray best visualizes the coalition. CT scan is definitive for bony coalitions. MRI evaluates cartilaginous and fibrous coalitions and secondary cartilage damage.

Conservative Treatment

Activity modification, custom orthotics with arch support, short-leg cast or boot for 4–6 weeks for acute pain episodes, and physical therapy. Conservative care works best for fibrous or cartilaginous coalitions without degenerative changes.

Surgical Treatment: Resection

Surgical resection (removal of the coalition bar with fat graft or extensor digitorum brevis muscle interposition) is the first-line surgery for symptomatic patients who fail conservative care. Results are excellent with pain relief and improved subtalar motion in 80–85% of appropriately selected patients. Resection is not indicated if significant subtalar arthritis is present — fusion becomes the appropriate option in that scenario.

The Anteater Nose Sign — and Why the Right X-Ray View Matters

A calcaneonavicular coalition is frequently missed on a standard two-view foot series, and the reason is purely geometric: on a straight lateral film the bar between the heel bone and the navicular is hidden behind other bone. The view that shows it is the 45-degree internal oblique, and if it is not requested it is usually not taken.

On that oblique, an elongated front process of the calcaneus reaching toward the navicular produces the anteater nose sign — a tapering beak of bone that, once seen, is difficult to unsee. It is one of the most reliable plain-film findings in paediatric foot radiology.

Two further points worth knowing:

• A fibrous or cartilaginous coalition can look nearly normal on X-ray. Not every coalition is solid bone. Fibrous and cartilaginous bars cause identical symptoms and restrict motion identically, but they do not produce a clean bony bridge on film. A normal X-ray in a child with a stiff, painful flatfoot does not close the question.
• CT defines it; MRI catches what CT misses. CT is the standard for mapping the size, position and surface area of the bar and for assessing whether the neighbouring joints have already developed arthritis. MRI is better for fibrous and cartilaginous coalitions and for detecting the bone marrow oedema that indicates the bar is actively symptomatic.

Why Symptoms Start Between 8 and 16 — and Not Before

Parents often ask why a condition present from birth only announces itself in middle childhood. The coalition is congenital, but it begins as cartilage. It ossifies — turns to bone — on a predictable schedule, and pain appears as it stiffens.

• Calcaneonavicular coalitions typically ossify between roughly 8 and 12 years.
• Talocalcaneal coalitions ossify later, around 12 to 16 years.

So a child who was fine at seven and is limping at ten has not developed a new problem. The existing bar has hardened, hindfoot motion has dropped, and the foot has lost its ability to absorb uneven ground. This is also why the diagnosis is missed in adults: the coalition was never identified, the foot adapted, and the presenting complaint decades later is arthritis or a chronically sprained ankle.

Peroneal Spastic Flatfoot: the Presentation That Gets Misdiagnosed

The classic picture is a rigid flatfoot in which the peroneal tendons on the outside of the leg feel tight and stand out, the heel is locked in an outward position, and any attempt to turn the sole inward is resisted and painful.

This is often labelled a muscle spasm or a stubborn ankle sprain, and treated with stretching that does not help. The spasm is protective — the peroneals are guarding a hindfoot that cannot move because two bones are joined. Treating the spasm without finding the coalition treats the alarm rather than the fire.

The distinguishing test is simple and takes seconds: ask the patient to rise onto their toes. In a normal flexible flatfoot the arch reappears and the heel swings inward. In a coalition the arch does not restore and the heel stays put. A flatfoot that does not correct on tiptoe should be imaged, not stretched.

The other tell is a history of repeated ankle sprains in a teenager. A hindfoot that cannot adapt to uneven ground transfers that demand to the ankle ligaments, which fail instead.

Resection Versus Fusion: What Actually Decides It

When bracing, orthotic control, immobilisation in a boot and activity modification have not settled things, surgery becomes reasonable. The choice is not made on symptoms alone — it is made on the CT.

Resection with interposition removes the bar and fills the gap with tissue so it cannot re-form. Fat harvested locally, or the extensor digitorum brevis muscle belly, is the usual interposition material; bone wax is sometimes used on the cut surfaces. This restores motion and is the preferred operation in the right patient. Calcaneonavicular coalitions respond particularly well — they are accessible, the bar is usually modest, and results in adolescents are good.

Fusion — subtalar or triple arthrodesis — is chosen when resection is unlikely to succeed. The findings that push toward it:

• The coalition involves more than roughly half the joint surface (most relevant for talocalcaneal bars).
• There is established arthritis in the subtalar or surrounding joints on CT.
• There is significant fixed heel valgus that resection alone will not correct.
• The patient is an adult presenting late, where the joints have already worn.

Where heel alignment is a substantial part of the problem, a calcaneal osteotomy is often added to whichever procedure is chosen, because leaving the heel in valgus loads the correction badly from the first step.

Recovery and Return to Sport After Resection

Recovery after resection is more forgiving than most families expect, but the early motion work is not optional — the whole point of the operation is movement, and a joint that is not moved scars back down.

• Weeks 0–2: splint or cast, elevation, non-weight-bearing.
• Weeks 2–6: boot with early range-of-motion exercises begun deliberately, progressing to weight-bearing as comfort allows.
• Weeks 6–12: out of the boot, physical therapy for hindfoot motion, peroneal strength and calf flexibility. Orthotic support if heel alignment needs help.
• Months 3–6: return to running and sport, guided by motion and strength rather than the calendar.

Re-formation of the bar is the main early risk and is the reason interposition material is used. Persistent pain after a technically good resection usually means either an incomplete excision or arthritis that was already present in a neighbouring joint.

Getting a Stiff Flatfoot Assessed

If a child or teenager has a flatfoot that does not restore on tiptoe, aches after sport, or has sprained the same ankle repeatedly, ask specifically for weight-bearing X-rays including a 45-degree oblique, and for CT if those are equivocal. Diagnosed before the joints wear, this is a very treatable problem. Balance Foot & Ankle sees patients in Howell (4330 E Grand River Ave, Howell, MI 48843) and Bloomfield (43494 Woodward Ave #208, Bloomfield Township, MI 48302). Call (810) 206-1402.

FAQs

Is calcaneonavicular coalition hereditary? Yes — it is an autosomal dominant condition. Other family members may have the same condition, often asymptomatically.

Sources

• Mosca VS. “Subtalar coalition in children.” Foot Ankle Clin. 2015;20(2):265-281.
• American Academy of Orthopaedic Surgeons (AAOS), OrthoInfo. “Tarsal Coalition.”
• Lemley F, et al. “Current concepts review: Tarsal coalition.” Foot Ankle Int. 2006;27(12):1163-1169.

In-Office Treatment at Balance Foot & Ankle

If home treatment isn’t providing relief for your flat feet, our podiatry team at Balance Foot & Ankle can help with same-day evaluations and advanced in-office care.

When a suspected coalition should be imaged

A calcaneonavicular bar most often declares itself between the ages of eight and fourteen, as the cartilaginous bridge ossifies and the hindfoot loses its remaining flexibility. The classic presentation is an adolescent with a stiff flat foot, repeated ankle sprains that never quite settle, and vague lateral or sinus tarsi pain that is worse on uneven ground. Two examination findings are worth checking before imaging: whether the arch reconstitutes when the patient rises onto the toes, and whether the heel inverts as they do. If neither happens, the foot is rigid and a coalition becomes considerably more likely. A standard series including an oblique view detects most calcaneonavicular bars, and CT defines them fully and picks up additional coalitions. Not every coalition needs surgery — many settle with orthoses, activity modification and a period of immobilisation — but a rigid flat foot in a teenager should never be dismissed as ordinary flat feet.

Balance Foot & Ankle sees patients at two Michigan offices: our Howell podiatry office, serving Livingston County, and our Bloomfield Township podiatry office, serving Bloomfield Hills, Birmingham, Pontiac and the rest of Oakland County. Dr. Tom Biernacki sees patients at both. Call (810) 206-1402 to book an appointment.