An accessory navicular is an extra bone, joined to the navicular by fibrous tissue or cartilage, that can develop in certain people. This bone can cause pain, and may be susceptible to injury.
An accessory navicular develops as a result of a congenital anomoly and is found more often in women. If the bone is large, it may rub against a shoe, causing pain. Because of its location, the posterior tibial tendon may pull on the bone during walking or running, causing the fibrous tissue that connects the accessory navicular to the navicular to tear and become inflamed.
The main symptom of an aggravated accessory navicular is pain, particularly in the instep. Walking can sometimes be difficult, and tight shoes may worsen the condition.
Treatment options for a painful accessory navicular can include anti-inflammatory medications, rest, arch support structures in the shoe, or use of a cast or splint. Severe cases may require surgery.