Accessory Navicular

The accessory navicular is an extra bone on the medial side of the navicular that can cause pain due to pressure on the lump from footwear (especially things like ice skates) and also be a factor in flat or overpronated feet due to changes in the pull of the tendon from the muscle that is the main supporter of the arch of the foot.

Most Useful Resources:
Accessory Navicular (PodiaPaedia)
Surgery for accessory navicular (Podiatry Arena)
Accessory navicular (Podiatry Arena)
Classification of the Accessory Navicular (Podiatry Ninja)
Accessory Navicular (Foot Health Forum)