A bunion is a bump, or fluid-filled sac, near the big toe joint. It may or may not involve movement of the big toe towards the second toe.

What is going on in the body?

A bunion or bunion deformity can be present from birth, but most often it occurs over time in an adult. Structural problems in the feet lead to irritation and deformity of the big toe joint.

The joint at the base of the big toe is made up of two bones. One extends from the arch of the foot and the other connects to the big toe. The two bones meet in a joint near the "ball" of the foot. In some persons, the bone from the arch tends to turn outward and the toe bone tends to turn inward, toward the second toe. This may be caused by a family tendency, unstable arches, or wearing ill-fitting shoes.

After many years, the joint becomes irritated. The irritation causes more bone to form in this area. This leads to irritation of the soft tissues that cover the bones. The whole area becomes inflamed, or swollen, and is pushed against the side of the shoe. This leads to more irritation and swelling and eventually to the painful condition known as a bunion.

What are the causes and risks of the condition?

Sometimes the irritation is so severe that the skin will blister or break open. This can lead to an infection. The biggest problem with bunions is pain. The pain may cause a person to become less active. The pain can also interfere with a person's daily activities.