Accessory navicular bone: not such a normal variant.

The accessory navicular is often erroneously considered as a normal anatomic and roentgenographic variant. Three distinct types of accessory navicular bones have been described. The type 2 and 3 variants have been associated with pathologic conditions such as posterior tibial tendon tear and painful navicular syndrome and therefore should not be arbitrarily dismissed as a roentgenologic variant in a symptomatic patient. The pathogenesis and radiologic findings are discussed and illustrated.