A tarsal coalition is an abnormal connection between two bones at the back of the foot, towards the ankle. This connection creates irregular forces on the bones, leading to pain and other problems. So what is a tarsal coalition, and what can you do about it?
The tarsal bones
The tarsal bones are seven bones in the middle and back of the foot. They provide up-and-down movement and inward (inversion) and outward (eversion) movement, working together for smooth function. Three — the navicular, calcaneus, and cuboid — are usually involved in a tarsal coalition.
What is a tarsal coalition?
A tarsal coalition occurs when two bones grow into each other and are joined by bone, cartilage, or fibrous tissue. The joined bones then move together rather than independently. The common sites are between the talus and calcaneus, and between the navicular and calcaneus.
About 5% of the population has a tarsal coalition, and around 50% of cases affect both feet.
How does a tarsal coalition present?
Coalitions usually become troublesome in children aged 9–16, though sometimes symptoms hold off until adulthood.
Teenagers typically report increasing ankle ache during and after activity. Pain sometimes follows a minor injury, such as an ankle sprain, and a coalition can cause repeated ankle sprains despite rehab. In more severe cases, children develop a sudden flat foot from muscle spasm.
A tarsal coalition can also present as a bump on the side of the foot.
How do we diagnose a tarsal coalition?
We examine the ankles and feet for signs of a coalition. Typically, the ankle and subtalar joints are stiff because the coalition prevents the bones from moving independently. We may also see a flat foot that doesn’t correct when rising onto the toes.
If we suspect a coalition, we image it: An
- X-ray of the ankle can show the coalition
- MRI gives more sensitive images, often revealing the abnormal connection with swelling on either side
- CT confirms whether the connection is bone or cartilage
How do we treat a tarsal coalition?
We only treat a coalition that’s causing symptoms, using a step-up approach from simple to interventional.
Conservative treatment
- Rest from high-impact sport for a short period; a boot if the pain is severe.
- A podiatry review for shoe insoles, which support and stabilise the foot and ankle
- Physiotherapy to strengthen the small foot muscles and the calf
- A subtalar/coalition cortisone injection to relieve pain in some cases
Surgical treatment
Surgery is considered only after conservative treatment fails. The choice depends on the coalition’s site, the symptom severity, and whether arthritis has developed:
- Resection is the commonest procedure — removing the coalition and replacing it with muscle or fat, preserving the bones’ normal movement and foot function.
- Fusion is used for larger, more severe coalitions, or where arthritis has developed, often with screws and plates.
More on the cortisone injection for tarsal coalition
We reserve cortisone injections for painful or severe cases that don’t respond to simple treatment, targeting the coalition between the two bones. We perform it under ultrasound guidance to improve accuracy and effectiveness — and one study found such an injection can delay surgery for up to two years.
Frequently asked questions about tarsal coalition.n
What happens if a tarsal coalition is left untreated?
If the pain stops you from playing sports and continues unchecked, arthritis can develop in the affected joints. So getting the pain under control matters.
Is a tarsal coalition genetic?
Often, yes — but not always. Some coalitions result from trauma or arthritis rather than genetics.
Can a tarsal coalition be treated without surgery?
Yes, in many cases. Rest, orthotics, physiotherapy, and sometimes an ultrasound-guided cortisone injection control symptoms without surgery. Surgery is reserved for cases that don’t respond to other treatments.
Why does a tarsal coalition cause ankle sprains?
The fused bones stiffen the hindfoot and reduce its ability to adapt to uneven ground, which can make the ankle roll more easily, so repeated sprains despite good rehab are a clue to an underlying coalition.
Does a tarsal coalition cause arthritis?
It can. Over time, abnormal forces across the subtalar joint can lead to subtalar arthritis, which is why early diagnosis and symptom control matter.
Final word from Sport Doctor London about tarsal coalition
Always suspect a tarsal coalition in a teenager or adult with persistent ankle pain after a minor injury. Early diagnosis means quicker treatment and a faster return to sport.
To book a foot and ankle assessment with Dr Masci in London, contact the team here or call +44 (0) 203 488 0350.
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