The os trigonum is an extra bone that develops behind the ankle bone. Often, people do not know they have this extra bone if it has not caused pain. However, when people develop pain around this extra bone, they have developed os trigonum syndrome.
Os trigonum syndrome is usually triggered by an injury, more commonly an ankle sprain. This syndrome is usually caused by repeated downward pointing of the toes, which is common among ballet dancers, soccer players and other athletes. Pointing the toes downward can result in a “nutcracker injury.” Like a walnut in a nutcracker, the os trigonum is pinched between the ankle and heel bones. As the os trigonum pulls loose, inflammation occurs. In the MRI above, the os trigonum is circled in red. The white area within the red circle indicates fluid/inflammation.
Symptoms of os trigonum syndrome include a deep pain in the back of the ankle especially when pushing off on the big toe when walking, pain when pointing the toes downward, swelling in the back of the ankle, and pain in the back of the ankle when touched.
Os trigonum syndrome can be misdiagnosed as Achilles tendonitis or an ankle sprain. Physical exam, xrays, and an MRI lead to a proper diagnosis. Conservative treatment include rest, immobilization,
anti-inflammatories, steroid injections, physical therapy, and cryotherapy. Surgical management of this syndrome includes removal of the os trigonum.
For more information please contact our office.