Accessory Navicular Syndrome (os tibiale externum)

What is an accessory navicular? 

An accessory navicular is an extra bone that someone is born with a birth and is attached to the navicular. The Classification for accessory naviculars is by Geist: Type 1 is a bone embedded in the posterior tibial tendon, type 2 is attached to the navicular by a fibrocartilaginous connection, and a type 3 is when the accessory bone is fused with the navicular. 

What are the symptoms of accessory navicular syndrome?

The pain associated with an accessory navicular typically is caused by rubbing due to the bony prominence of the accessory bone and/or posterior tibial tendonitis. Symptoms are visible prominence on the medial side of the foot in the area of the navicular, redness and swelling around the prominence, and pain along the area of the bony prominence especially after activity. 

How to diagnosis accessory navicular syndrome?

Clinically there is typically an obvious bony prominence and then an Xray is often used to confirm. An MRI may be used for advanced imaging. 

How to treat accessory navicular syndrome?

RICE, immobilization, orthotics, and physical therapy are the first line of treatment. If pain persists then surgery will be done and this involves removing the bony fragment and possible reattachment/repair of the posterior tibial tendon to the navicular. Patient’s with accessory naviculars sometimes have flat feet and are often addressed at the same time with surgery.