My daughter's ballet teacher had to quit dancing because of a condition called os trigonum syndrome. What is this?

The os trigonum is a bump on the side of the talus bone in the ankle. It’s sometimes also called the lateral talar tubercle. The os trigonum syndrome is a painful condition of the ankle most common in ballet dancers. It’s also known as posterior ankle impingement (PAI).

The dancer’s repeated motions and jumping cause a bone contusion or “bruise.” There is usually fluid around the nearby tendon. Of course, ankle pain is the most common symptom. This occurs along the back or outside (lateral) edge of the ankle.

Treatment is often rest and drugs for inflammation. Surgery to remove the bump on this bone can be done. The doctor often releases the tendon at the same time. After rehab, the dancer is usually able to return to previous levels of dancing.