Our knowledge of orthopaedics. Your best health.

The bones of the feet are commonly divided into three parts: the hindfoot, midfoot, and forefoot.

Seven bones — called tarsals — compose the hindfoot and midfoot. Coalitions can happen between any of the bones, but the calcaneus, talus, and navicular are most commonly involved in tarsal coalitions.

The calcaneus, talus, and navicular are the bones most often affected by tarsal coalition.

In human development, the bones of the hindfoot are supposed to divide out into separate ones. However, this does not always happen, and a tarsal coalition occurs when two bones have an abnormal connection. This can be a bridge of bone, cartilage, or fibrous tissue. These bridges are often referred to as "bars" and they can cover just a small amount of the joint space between the bones, or a large portion of the space.

The two most common sites of tarsal coalition are:

• Between the calcaneus and navicular bones (calcaneonavicular coalition)
• Between the talus and calcaneus bones (talocalcaneal coalition)

However, other joints can also be affected.

This X-ray image of a right foot shows a tarsal coalition between the navicular bone and the calcaneus bone.

Courtesy of Texas Scottish Rite Hospital for Children

It is estimated that one out of every 100 people may have a tarsal coalition. In about 50% of cases, both feet are affected. The exact number of people with the disorder is hard to determine because many coalitions never cause noticeable symptoms. In other words, there are many people who have this condition and do not know it.

Although the coalition forms before birth, its presence is usually not discovered until late childhood or adolescence. This is usually because the abnormal connection does not cause pain or symptoms until the child gets a little older.

In babies, the foot contains a higher percentage of soft, growing cartilage. As a child grows, this cartilage mineralizes (ossifies), resulting in hard, mature bone. If a coalition exists, it may harden, too, and fuse the growing bones together with a solid bridge of bone or fibrous tissue similar to a scar. The ossification of the coalition typically happens between ages 8 and 16, depending upon which bones are involved. 

As the coalition turns to bone, the foot becomes stiffer and can start causing pain and other symptoms. Over time, the stiffness of the foot can lead to arthritis.

Many tarsal coalitions are never discovered because they do not cause symptoms or any obvious foot deformity. When symptoms do occur, they may include:

• Stiff, painful feet. The pain usually occurs below the ankle around the middle or back half of the foot.
• A rigid, flat foot that makes it difficult to walk on uneven surfaces. The ankle may have to roll more to make up for the lack of foot motion. This can cause repeated ankle sprains.
• Increased pain or a limp with higher levels of activity.

Tarsal coalitions require treatment only if they are causing symptoms.

Surgical Treatment

When nonsurgical treatments are not effective at easing pain or improving function, your child's doctor may consider surgery.

The surgical procedure the doctor recommends will depend on the size and location of the coalition, and whether the joints between the bones show signs of arthritis.

• Resection (Removing the Coalition). In this procedure, the coalition is removed and replaced with muscle or fatty tissue from another area of the body. This is the most common surgery for tarsal coalition because it preserves normal foot motion and successfully relieves symptoms in most patients who do not have signs of arthritis.
• Flatfoot Reconstruction. Removal of the coalition alone does not correct the flat shape of the foot. If the flatness is severe enough to also cause symptoms, correction of foot alignment may also be done at the time of the coalition resection. This usually involves cutting and realigning the bones to rebuild an arch.

These CT cross-section images show a patient with coalitions between the calcaneus and talus in both feet. At the time of this scan, the coalition on the left foot had been resected, and the right foot was awaiting the procedure.

Reproduced with permission from Pierz KA Tarsal coalition. Orthopaedic Knowledge Online Journal 8/1/2009. Accessed December 2013.

• Fusion. For larger, more severe coalitions that cause significant deformity and also involve arthritis, joint fusion may be needed. The goal of fusion is to limit movement of painful joints and place the bones in the proper position. In fusion for tarsal coalition, the bones may be held in place with large screws, pins, or screw-and-plate devices.

• Depending on the type and location of the surgery, a cast will be required for a period of time to protect the surgical site and keep your child from putting weight on the foot.
• When the cast comes off, it will likely be replaced with a walking boot, and the doctor may recommend physical therapy exercises to begin restoring range of motion and strength. The doctor will determine when it is safe for your child to begin putting weight on the foot. Arch supports or orthotics may also be helpful in supporting the foot joints, even after surgery.
• Although it may take several months to fully recover, most patients experience pain relief after surgery.