Os Trigonum Syndrome
Foot & Ankle Care of Colorado
The os trigonum is an accessory bone that sometimes develops behind the ankle bone (talus), connected to the talus by a fibrous band. This condition is congenital, meaning it is present at birth, and becomes evident during adolescence when a portion of the talus does not fuse with the rest of the bone, resulting in a small extra bone. Only a small number of people have this extra bone.
Causes of Os Trigonum Syndrome
Os trigonum syndrome occurs when an individual with the extra bone sustains an injury to its attachment, such as a sprained ankle. It often results from repetitive stress on the ankle, including activities like:
- Frequently pointing the toes downward, as in dancing.
- Repeatedly kicking a ball, as in soccer.
- Pushing off the back of the ankle, as in running.
With injury or overuse, the extra bone can become pinched or pull away from its attachment point. This can stretch and tear the surrounding tissue, causing irritation, inflammation (swelling), and symptoms.
Os Trigonum Syndrome Symptoms
The signs and symptoms of os trigonum syndrome may include:
- 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 Diagnoses
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.
Nonsurgical Treatments
Relief of the symptoms is often achieved through treatments that can include a combination of the following:
- Rest. It is important to stay off the injured foot to let the inflammation subside.
- Immobilization. A walking boot is often used to restrict ankle motion and to allow the injured tissue to heal.
- Ice. Swelling is decreased by applying a bag of ice covered with a thin towel to the affected area. Do not put ice directly against the skin.
- Oral medication. Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, may be helpful in reducing the pain and inflammation.
- Injections. Sometimes cortisone is injected into the area to reduce the inflammation and pain.
When Is Surgery Needed?
Most patients’ symptoms improve with nonsurgical treatment. However, in some patients, surgery may be required to relieve the symptoms. Surgery typically involves removal of the os trigonum, as this extra bone is not necessary for normal foot function.
