There are 26 bones in the human foot. Some people have extra bones (accessory ossicles) which are usually congenital (present at birth) but may also be due to previous trauma. These extra bones, which can occur with any bone in the foot, can be painless (asymptomatic) and are only noticed when the foot is x-rayed. Sometimes they are painful and cause significant discomfort. This pain can usually be treated by the foot and ankle surgeon using a variety of non-surgical measures, although sometimes the extra bones may need to be surgically removed.
To learn more, read Accessory Navicular Syndrome, Os Trigonum Syndrome.