Items that are meant to be stuck together: stapled sheets of paper, peanut butter and jelly sandwich, duct tape and pretty much anything. Notice that ‘bones of the ankle’ are not on that list. However, there is a rare condition called tarsal coalition where two of the many bones of the ankle are fused together from birth. It is estimated that this phenomenon occurs in only about one percent of the population.
The union between the bones can be made up of bone, cartilage, or fibrous tissue, but the condition only causes symptoms when the soft tissue of the coalition becomes bony, which happens between 8-16 years of age. Before this time, the flexible nature of the coalition allows some degree of motion at the joint but afterwards symptoms can include pain, stiffness, and deterioration of athletic performance. However, these symptoms are often not severe enough to warrant a visit to the doctor until trauma to the ankle causes a flare-up of pain.
In athletes, tarsal coalitions often cause recurrent ankle sprains because the abnormal joint cannot transfer the force of athletic activity to the other joints, so the surrounding ligaments take the strain, causing injury.
In treatment of a tarsal coalition, a trial of non-operative treatment is attempted before resorting to surgery. These conservative treatment options includes anti-inflammatory medication, orthotics (shoe inserts), and for severe symptoms, 6 weeks in a short walking cast may be used for immobilization.
If these treatments do not succeed and pain continues, surgical intervention is needed, which usually involves taking the coalition out and putting soft tissue between the bones.
If you think you have tarsal coalition or that your child’s ankle bones are not developing properly, you may want to consult an orthopedic foot specialist for treatment.
– David A. Porter M.D. PhD