The navicular bone is a normal bone in the foot that is critical to the function of the foot. One of the main tendons of the foot, the posterior tibial tendon, inserts into this bone and balances the foot by its pull in this area.
An accessory navicular is an extra bone or piece of cartilage in this region of the foot that may be an outgrowth of the normal navicular bone or a separate small bone adjacent to the normal navicular bone.
Most people who have an accessory navicular bone are unaware of its presence as it is usually not painful. For some, however, this extra prominence on the inside of the foot results in irritation and pain caused by the rubbing between the normal navicular and accessory navicular bones. Weakness of the foot may also occur because of the abnormal function and insertion of the posterior tibial tendon may be present.
For many patients, immobilization in a cast may cause resolution of symptoms. Orthotics may also be of benefit. For those with continued pain, surgical removal of the accessory navicular bone with reattachment of the posterior tibial tendon may be necessary.