accessory bone

These bones do not perform any necessary function and are often called accessory bones.

The thumb has several associated accessory bones.

Named accessory bones include:

An accessory bone is a bone which does not occur frequently in the body but is still present in a significantly large number of people.

Examples of accessory bones include the os trigonum ("accessory talus") which if present in the foot typically lies posterior to the talus.

An accessory navicular bone is an accessory bone of the foot that occasionally develops abnormally in front of the ankle towards the inside of the foot.

Occasionally accessory bones are found in the carpus, but of more than 20 such described bones, only four (the central, styloid, secondary trapezoid, and secondary pisiform bones) are considered to be proven accessory bones.