A bunion, clinically known as hallux abducto valgus, is one of the most common structural deformities of the foot and ankle. By appearance, bunions are a small to large bump on the inside of the foot at the base of the big toe. They begin with the big toe leaning inward toward the second toe. This movement gradually changes the angle of the corresponding bones, causing misalignment and producing the characteristic bump. As bunions progress, they can become sore, inflamed and increasingly painful.