Extra Foot Bone (Accessory Navicular)

Information for Families – Accessory Navicular Bone

What is an accessory navicular?
An accessory navicular is an extra bone (ossicle) which is found next to the navicular bone (one of the bones on the inside of the foot). It is the most common accessory bone in the foot occurring in between 4-14% of the population.

What is the cause?
This condition tends to run in families so may have a genetic basis.

What are the symptoms?
It tends to cause problems in adolescence and is often related to having flat feet. The extra bone can become sore as it causes a painful bump that can rub on the inside of shoes

How is it diagnosed?
It is usually easy to feel the bump and the diagnosis is confirmed with an X ray – see yellow circle shown.

What is the natural history?
In the vast majority of cases most people who have these extra bones are asymptomatic. In those patients who do have symptoms, they seem to come and go as they tend to be activity related.

What are the treatments?
Non operative treatment – These are always tried first and often relieve symptoms:

• Restricting those particular activities (ie: certain sports) that aggravate symptoms

• Custom made insoles (to fit inside shoes) – to take pressure off that area (orthotics)

• A below knee plaster cast is sometimes used for 2 weeks to rest the foot and let the associated inflammation settle right down

If after a period of several months and non operative treatments have not helped then surgery is considered.

What is involved with the operation?
The operation is usually straightforward and involves excising the additional bone, through an incision over the bump, on the inside of the foot. It has a success rate of about 90% in taking the symptoms away, with little risk involved. We will discuss this in detail with you if required.