What is an accessory bone?

An accessory bone is an extra bone. These can form anywhere in the foot but are usually located within a tendon where the tendon crosses at an angle to another bone. However, they can form between two bones or be an extension of a normal bone that has not fully united to it during development. We call these bones accessory ossicles.

The most common accessory ossicles of the foot are the os peroneum, the os navicularis, and the os trigonum. Of these, the os navicularis may be visible where the major tendon, the posterior tibial tendon, inserts into your arch.

These ossicles are not usually a problem but can become irritable with injury to the foot. Treatment can include rest, ice, elevation, and immobilization. This usually requires a boot extending up to the knee. The treatment period may require several weeks to achieve complete healing. If conservative care doesn’t alleviate symptoms, surgery to remove the bone is recommended.

It’s important to distinguish the sesamoid from a bone spur and be sure that no degeneration has occurred to joints in the area of ossicle. Xrays and CT scan may be required to evaluate your condition completely. Surgery is generally very successful with complete recovery taking from three to six weeks.

To make an appointment with one of our Seattle podiatrists, call us at 206-368-7000 or request an appointment online.

Dr. Rion Berg
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A podiatrist in North Seattle treating families for over 40 years.