Bone, Joint and Muscle Conditions

Tarsal Coalition

What Is Tarsal Coalition?

Rigid flatfeet with tarsal coalition. Photos by Vincent S. Mosca, MD.

Rigid flatfeet with tarsal coalition.

Tarsal coalition is a type of flatfoot. It occurs when two or more of the tarsal bones, found in the middle and back of the foot, join together. These bones are usually separate.

Tarsal coalition belongs to the category of flatfoot called rigid flatfoot. The feet of children with tarsal coalition look the same as the feet of children with other forms of flatfoot. Their feet angle outward from the leg and they do not have an arch in the middle. But feet with a tarsal coalition are stiff, not flexible like some other forms of flatfoot.

Unlike with other forms of flatfoot, babies are not born with a tarsal coalition. Instead, their feet flatten out as they get older, usually between the ages of 8 and 16.

Each of the tarsal bones has a name. The most common sites for a tarsal coalition are between the calcaneus and navicular bones and between the talus and calcaneus bones.

About half of cases involve the first set of bones and about half involve the second set. In some cases, both sets of the bones are joined together in the same foot.

Tarsal Coalition in Children

Rigid flatfeet with tarsal coalition with heels lifted. Photos by Vincent S. Mosca, MD.

Rigid flatfeet with tarsal coalition with heels lifted.

About 1% to 2% of people have tarsal coalition. It is an inherited (genetic) condition. Parents with tarsal coalition can pass it on to their children. It is not associated with any other medical problems.

The good news is that only about a quarter of people who have tarsal coalition have problems with it or need treatment. Of those who need treatment, a third to half are helped without surgery.

Tarsal Coalition at Seattle Children's

Tarsal coalition is one of the conditions treated by the experts in our Foot and Ankle Deformities Program.

Dr. Vincent S. Mosca, chief of foot and ankle medicine at Seattle Children's, is a leader in clinical research on foot problems in children and teenagers.

Flatfoot, including tarsal coalition, has been a focus of his work. He recently has worked on surgical procedures for the most complex and severe cases of tarsal coalition. His procedure is becoming the preferred method to treat the problem.