 When it is symptomatic, surgery may be necessary.Accessory navicular bone may cause a continuous stretch and stress on the tibialis posterior tendon which can progress to chronic disabling pain and may cause tendon rupture or secondary flat foot deformity, when this occurs this condition is commonly known as accessory navicular syndrome.Other conditions which closely mimic the symptoms of an accessory navicular bone include plantar fasciitis, bunions and heel spurs.