The joint at the base of the great toe is incredibly complex. Here the bones, tendons and ligaments work together to transmit and distribute the body's weight, especially during movement. Should this joint become abnormally stressed over an extended period of time, a bunion may result.

A bunion (from the Latin "bunion," meaning enlargement) is a protuberance of bone or tissue around the joint. The enlargement occurs either at the base of the great toe or on the outside of the foot, at the base of the little toe. This is called a "bunionette" or "tailor's bunion."

Bunions at the base of the great toe usually begin when the big toe starts moving toward the smaller toes. This crowding puts pressure on the joint, pushing it outward. The movement of the joint in this outward direction starts the formation of a bunion.

A common deformity of the big toe joint, bunions occurs mostly amongst women who wear tight, pointed, confining or high heeled shoes. High heels can e especially stressful on the joints of the foot because all of the body's weight rests there; the foot is then forced into a narrow, pointed toe box, compounding the problem. Older people are also vulnerable to bunions because of the higher incidence of arthritis affecting the big toe joint.

Propensity for the deformity is hereditary. People with flat feet or low arches are more prone to develop the problem than those with higher arches. A fracture or break into the joint can also lead to arthritic changes and the development of bunion deformities with limited range of motion.