A bunion is a bone deformity caused by an enlargement of the joint at the base and side of the big toe (metatarsophalangeal joint). Bunions form when the toe moves out of place. The enlargement and its protuberance cause friction and pressure as they rub against footwear. Over time, the movement of the big toe angles in toward the other toes, sometimes overlapping a third toe (known as Hallux Valgus). The growing enlargement or protuberance then causes more irritation or inflammation. In some cases, the big toe moves toward the second toe and rotates or twists, which is known as Hallus Abducto Valgus. Bunions can also lead to other toe deformities, such as hammertoe.
Many people with bunions suffer from discomfort and pain from the constant irritation, rubbing, and friction of the enlargement against shoes. The skin over the toe becomes red and tender. Because this joint flexes with every step, the bigger the bunion gets, the more it hurts to walk. Over time, bursitis or arthritis may set in, the skin on the bottom of the foot may become thicker, and everyday walking may become difficult—all contributing to chronic pain.
Wearing shoes that are too tight is the leading cause of bunions. Bunions are not hereditary, but they do tend to run in families, usually because of a faulty foot structure. Foot injuries, neuromuscular problems, flat feet, and pronated feet can contribute to their formation. It is estimated that bunions occur in 33 percent of the population in Western countries.