Tarsal coalition is an abnormal connection that forms between two or more bones in the back of the foot. This condition is congenital, meaning it is present at birth and arises from an error during fetal development where the bones fail to properly separate. The connection itself can be composed of solid bone, flexible cartilage, or fibrous tissue. While it affects an estimated 1-6% of the population, many individuals with a tarsal coalition never experience symptoms or require diagnosis.
Anatomy and Types of Tarsal Coalition
The foot contains a cluster of seven bones known as the tarsal bones, which make up the hindfoot (heel area) and midfoot (middle of the foot). A tarsal coalition is the result of a genetic mutation that interferes with the normal separation of these bones during embryonic development. This failure of segmentation leads to an improper linkage, which can range from a fibrous connection to a solid bony bridge. This abnormal connection restricts movement in the affected joints.
While several combinations are possible, two types of tarsal coalition are most common. The first is a calcaneonavicular coalition, where the bridge forms between the calcaneus (heel bone) and the navicular bone, which is located on the top-inner side of the foot. The second common type is a talocalcaneal coalition, occurring between the talus bone (the lower bone of the ankle) and the calcaneus. In about half of diagnosed cases, coalitions are present in both feet.
Common Symptoms
Although tarsal coalition is present from birth, symptoms do not appear until late childhood or adolescence. This delay occurs because the connecting tissue, which is initially flexible cartilage, begins to harden into bone—a process called ossification. The age of onset often corresponds to the specific bones involved, with calcaneonavicular coalitions becoming symptomatic between ages 8 and 12, and talocalcaneal coalitions between 12 and 15.
The most frequent symptom is a deep, aching pain located just below the ankle, in the midfoot or hindfoot area. This discomfort often worsens with increased physical activity and can be accompanied by a feeling of stiffness in the foot. Individuals may also experience leg fatigue, muscle spasms in the peroneal tendons on the outside of the ankle, and difficulty walking on uneven surfaces. A characteristic sign that develops is a rigid, spastic flatfoot, which can increase the risk for recurrent ankle sprains.
The Diagnostic Process
Diagnosing a tarsal coalition begins with a thorough physical examination by a healthcare provider. The physician will assess the foot’s range of motion, paying close attention to the subtalar joint, which is located just below the ankle joint and is responsible for side-to-side movement. An indicator is rigidity and a limited or absent range of motion in this joint, often coupled with a visible flatfoot deformity. The doctor will also check for tenderness and pain in the hindfoot and midfoot.
Imaging studies are used to confirm the presence and type of coalition. The process starts with X-rays of the foot and ankle, which are effective at identifying many coalitions, particularly the calcaneonavicular type. For a more definitive diagnosis, a CT scan is often considered the best imaging tool. A CT scan provides detailed, cross-sectional images of the bones, allowing the surgeon to see the precise location, size, and bony nature of the coalition. An MRI may also be used to evaluate the coalition if it is still composed of cartilage or fibrous tissue and to assess the health of surrounding soft tissues.
Conservative Management Options
For symptomatic cases, treatment begins with conservative, non-surgical methods aimed at relieving pain and improving function. These approaches do not eliminate the coalition but can effectively manage the symptoms. A primary strategy involves rest and activity modification, which means temporarily stopping high-impact activities that stress the foot for three to six weeks to allow inflammation to subside.
Other methods are also used to support the foot and limit painful motion:
- Custom orthotics or shoe inserts to stabilize the foot and redistribute pressure away from the affected joints.
- A short period of immobilization using a walking boot or a cast to completely rest the foot and calm symptoms.
- Physical therapy to help stretch and strengthen surrounding muscles.
- Over-the-counter anti-inflammatory medications to help reduce pain.
- Corticosteroid injections directly into the affected area for more persistent pain.
Surgical Interventions
Surgery is considered when conservative treatments fail to provide lasting relief from pain. The most common surgical procedure is a resection, which involves the complete removal of the abnormal bone or tissue bridge connecting the tarsal bones. After the coalition is removed, a piece of muscle or fatty tissue from another part of the body is often placed into the space to prevent the bridge from growing back. This procedure is designed to restore motion between the bones and alleviate pain, with younger patients having better outcomes.
In more severe cases, particularly when the coalition is very large or when significant arthritis has developed in the joint, a procedure called fusion, or arthrodesis, may be recommended. During a fusion, the surgeon removes the painful joint surfaces and permanently joins the bones together using screws or plates. This procedure eliminates painful motion entirely, sacrificing mobility for pain relief. Recovery from surgery varies, with resection often allowing for a quicker return to activity compared to a fusion, which requires a longer period of immobilization in a cast.