What is Os Trigonum? The os trigonum is an extra (accessory) bone that sometimes develops behind the ankle bone (talus). It is connected to the talus by a fibrous band. The presence of an os trigonum in one or both feet is congenital (present at birth). It becomes evident during adolescence when one area of the talus does not fuse with the rest of the bone, creating a small extra bone. Only a small number of people have this extra bone.
What is Os Trigonum Syndrome? Often, people don’t know why they have an os trigonum if it hasn’t caused any problems. However, some people with this extra bone develop a painful condition known as os trigonum syndrome. Os trigonum syndrome is also frequently caused by repeated downward pointing of the toes, which is common among ballet dancers, soccer players and other athletes. For the person who has os trigonum, pointing the toes downward can result in a “nutcracker injury.” Like an almond in a nut cracker, the os trigonum is crunched between the ankle and heel bones. As the os trigonum pulls loose, the tissue connecting it to the talus is stretched or torn and the area becomes inflamed.
Signs and Symptoms: The signs and symptoms of os trigonum syndrome may include:
Deep, aching pain in the back of the ankle, occuring mostly when pushing off on the big toe (as in walking) or when pointing the toes downward.
Tenderness in the area when touched.
Swelling in the back of the ankle.
If you believe you have os trigonum, call our office and often receive the same day appointment!