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Os Peroneum (Accessory Bone)

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What is an Os Peroneum?

An Os Peroneum is the name given to an accessory bone or accessory ossicle on the outside of the foot.

Accessory bones are small, extra pieces of bone that develop in some people. They usually sit in certain areas of the body close to other bones, and most of the time don’t cause pains or problems. If we did a full body x-ray of you now, we could find some of these you didn’t know you had.

They are usually rounded in appearance as opposed to fragments of bone you may get if you have had a fracture.

Sometimes in the feet, they can become a problem. One common area is the outside of the foot and ankle, which is where an Os peroneum can lie. The peroneal tendons which run down the outside of the ankle and into the foot can become irritated by the accessory bone.

How can I help myself?

If aggravation occurs, it can settle down with conservative treatment, however, professional assessment and diagnosis is important because lots of things can occur in this area of the body.

The following links may be useful:


Ice Therapy

Anti-inflammatory and pain-relieving medication

When to see a Podiatrist?

A Podiatrist can assess the area to see if the problem could be an Os Peroneum or perhaps a different problem in this area. Plain x-rays can be used to show if there is an ossicle. Several x-ray angles may be needed to help determine the location.

Some people may present with Peroneal Tendon Pain which could be caused by an Os Peroneum, however not every patient needs to have an x-ray if the tendon pain settles down with conservative treatment.

Footwear changes, rest, foot orthoses or braces and exercises may be advised or prescribed. Steroid Injections and sometimes surgery may be needed if symptoms persist.

If you book an appointment, it is wise to take the footwear you wear day to day is that the podiatrist can see this.

Os Peroneum
Os Peroneum