O is for Os Trigonum

May 17, 2013

The Os Trigonum is a small bone at the back of the ankle joint in some people that can be painful.

The os trigonum is an extra bone located in the back of the ankle, specifically at the posterior aspect of the talus bone. It is a small, accessory bone that is present in a small percentage of individuals. The term “os trigonum” means “triangular bone” in Latin, as it has a triangular shape.

The os trigonum typically develops as a separate ossification center during skeletal development and fails to fuse with the talus bone in some individuals. It is considered an accessory bone because it is not present in everyone and does not play a significant role in the normal functioning of the ankle.

In some cases, the os trigonum may not cause any symptoms or issues. However, it can be a source of pain and discomfort in certain circumstances. The presence of an os trigonum can potentially lead to a condition called os trigonum syndrome. This occurs when the bone becomes irritated, inflamed, or compressed, causing pain and limited range of motion in the ankle. Activities that involve repetitive pointing of the toes, such as ballet or certain sports, may aggravate the condition.

Treatment for os trigonum syndrome typically begins with conservative measures, such as rest, ice, physical therapy, and anti-inflammatory medications. If conservative treatments do not provide relief, more advanced interventions may be considered, including immobilization with a cast or boot, corticosteroid injections, or in rare cases, surgical removal of the os trigonum.


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