Os Trigonum Syndrome and Posterior Ankle Impingement

What Is the Os Trigonum?  

Os trigonum is an extra bone that can develop behind the ankle bone (talus). It is connected to the talus by a fibrous band of tissue. 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.

Signs & Symptoms of Os Trigonum Syndrome

• Deep, aching pain in the back of the ankle, occurring 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

Os trigonum syndrome is usually triggered by an injury, such as an ankle sprain. The 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 an os trigonum, pointing the toes downward can result in a “nutcracker injury.” Like an almond in a nutcracker, 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.

Diagnosis

Os trigonum syndrome can mimic other conditions, such as an achilles tendon injury, ankle sprain, or talus fracture. Diagnosis of os trigonum syndrome begins with questions from the doctor about the development of symptoms. After the foot and ankle are examined, x-rays or other imaging tests are often ordered to assist in making the diagnosis.

Make sure to come see Dr. Jonathan Pajouh regarding any issue or concerns you may have. Please call and make an appointment today: 972-726-6464