Tarsal coalition: symptoms, diagnosis and treatment

The tarsal bones make up the back and middle of the foot. In a tarsal coalition, two of these bones are joined by a bridge instead of moving separately. The connection can be bone, cartilage or fibrous tissue, or a mixture.

The Royal Orthopaedic Hospital (ROH) lists the most common types. A talocalcaneal (subtalar) coalition joins the heel bone and the talus above it. A calcaneonavicular coalition joins the heel bone and the navicular in front of it. A talonavicular coalition, between the talus and the navicular, is rare.

Kent Community Health NHS Foundation Trust gives approximate shares of 48 per cent calcaneonavicular and 44 per cent talocalcaneal, and says it affects men more than women.

Both NHS trust leaflets describe a failure of the cells between certain bones to separate while the baby develops in the womb. The ROH says it is thought to be due to an inherited, genetic abnormality, and Kent Community Health says it can also be found in first-line relatives in a notable share of cases.

So a coalition is not caused by anything a person did, and it cannot be prevented. What changes over time is how the connection behaves as it hardens.

The ROH says pain usually occurs below the ankle in the middle or back half of the foot. It often starts when the connection stiffens, a process called ossification. This is usually between ages 8 and 12 for talocalcaneal coalitions and 12 to 15 for talonavicular ones. Kent Community Health gives slightly different age bands and notes that coalitions become solid at different times.

In adults, pain may follow an injury such as an ankle sprain, or the development of arthritis in nearby joints. The coalition may be linked with a stiff flatfoot.

The ROH says pain may come from the coalition, from the peroneal tendons on the outside of the ankle which can shorten and spasm, and from strained ligaments and irritated joints. Kent Community Health says 20 to 30 per cent of patients can develop muscle spasms on the outside of the leg in response to pain.

• Pain below the ankle or in the midfoot, often after activity.

• Frequent ankle sprains or a feeling of the ankle giving way.

• Foot stiffness and difficulty walking on uneven ground.

• A flat foot that stays flat when standing on tiptoe.

• Often both feet are affected, though symptoms may be on one side.

According to the ROH, diagnosis combines examination of how the joints move and imaging. A typical finding is a low-arched, stiff flat foot that does not correct when you go up on tiptoe.

X-rays can help, but the ROH says a high-definition CT or MRI scan is often needed to show the size of the coalition and to plan surgery. Kent Community Health pictures X-rays, MRI and sclerosis (whitening) around the affected joint as examples of what imaging shows.

BOFAS, the British Orthopaedic Foot and Ankle Society, lists tarsal coalitions among the findings that weight-bearing X-rays can reveal when assessing nerve-related heel and ankle pain.

The ROH lists the non-operative options: limiting high-impact activity for a few weeks, physiotherapy for stretching and strengthening, footwear changes such as an ankle boot or a rocker-bottom shoe, orthotics such as braces or insoles, anti-inflammatory pain relief, steroid injections for some people, and a period of immobilisation for a few weeks.

Kent Community Health describes a similar approach: a below-knee weight-bearing cast for four to six weeks to settle pain, insoles to support the foot, and, when peroneal spasm is present, an injection behind the knee that numbs the leg and reduces the spasm so the foot position can be checked for casting or insole therapy.

The ROH says surgery is normally considered when non-operative treatment fails and there is significant pain and functional limitation, such as struggling to walk or play sport. It involves either removing the coalition (resection) or fusing the joints.

For a calcaneonavicular coalition, removal is generally the operation, with a graft or muscle placed in the gap to reduce the chance of regrowth. Kent Community Health says this can be done under local anaesthetic, with a below-knee cast for four to six weeks and physiotherapy afterwards.

Talocalcaneal coalitions may be removed if they are less than about half the joint surface and there is little arthritis. Heel realignment may be needed too. If arthritis is present or the coalition is large, joint fusion may be advised. The ROH says a fusion aims to trade painful movement for less pain, and that after surgery the foot will remain stiffer than a normal foot.

After resection, the ROH says patients are usually in a non-weight-bearing cast for about 2 weeks, then a walking boot for about 4 weeks, with physiotherapy. Swelling and low-level discomfort can continue for 6 to 12 months. Driving is normally possible after about 6 weeks, and return to work varies from 3 to 4 weeks for a desk job to 8 to 12 weeks for manual work. After fusion Kent Community Health describes up to 8 to 10 weeks non-weight-bearing in a cast.

Risks include infection, nerve or tendon injury, wound problems, blood clots and anaesthetic risks, and for resection incomplete or excessive removal and recurrence. The ROH quotes recurrence of about 10%. Younger patients often make a full recovery after resection, whereas ongoing symptoms are more likely with talocalcaneal resection and in older patients.

Foot and ankle problems like this are usually assessed by a GP, podiatrist or musculoskeletal service, with referral to orthopaedic foot and ankle or podiatric surgery teams if surgery is being considered. Kent Community Health provides it through a podiatric surgery service.

A private foot and ankle specialist can arrange MRI or CT quickly and explain the options. As surgery cannot make the foot completely normal, it is worth asking about expected outcomes, recovery time and what non-operative options remain.