Os Trigonom

What is an Os Trigonom?

An Os Trigonom is an accessory bone that lies posterior to the talus. It can sometimes cause irritation at the back of the ankle (Posterior ankle impingement))

Image result for os trigonum syndrome

The signs and symptoms of os trigonom syndrome include:

  • Redness and swelling of the bony prominence
  • Vague pain or throbbing in the back of the Achilles, usually occurring during or after periods of activity

Ultrasound examination at The Ankle and Foot Centre can assist in diagnosing this problem.

Causes of Os Trigonom Syndrome

Some people will have always had this extra bone present in their foot but certain factors may cause to bone to become symptomatic including:

  • Trauma – acute trauma to the bone can cause irritation
  • Footwear – shoes that are too high can cause impingement of the posterior aspect of the ankle joint
  • Flat feet-

Diagnosis of pain associated with the Os Trigonom

Diagnosis is usually based or symptoms and a complete assessment of your foot and ankle.

At the Ankle, Foot and Orthotic Centre we are able to provide additional information about the presence of an accessory navicular bone with ultrasound imaging.


Treatment of Os Trigonom Syndrome

Treatment of accessory navicular bone depends on the cause of the irritation. If the cause of irritation is from footwear then footwear adjustment may be necessarily in these cases.

  • Avoid wearing high healed shoes
  • Orthotics with a medial rearfoot post
  • Lace up ankle brace
  • Surgery



The Ankle and Foot Centre’s Northcote Podiatrists can help you with all lower limb complaints, including pain from an accessory bone . Make an appointment to get your foot and ankle pain under control.