A bunionette is not a growth or cyst as some people believe. It is actually a protrusion of the joint that connects the foot to the little toe. The bump is caused by a misalignment of the bone in the foot that forces the joint outward and the pinky toe in towards the other toes. When the bump rubs against the inside of a tight-fitting shoe, a sore spot or callus can develop on the bunionette.

The most common cause of this deformity is a faulty mechanical structure of the foot, which runs in families and can be inherited by both men and women. However, wearing shoes that don't allow enough space for all of the toes to lie flat can make the structural problem worse. High-heel shoes or shoes with narrow pointy toe boxes can rub against the bunionette and cause redness, swelling, and pain.