Bunion on the foot of a middle-aged man. A bunion (hallux valgus) is a swollen pad overlying a deformity of the joint between the big toe and the first metatarsal bone in the foot. The big toe often becomes bent inwards, compressing the other toes. Bunions are typically caused by chronic pressure from ill-fitting shoes. The bunion often becomes inflamed and painful. In the early stages of its formation, a change of footwear and rest may be able to treat the condition, but more advanced cases require surgical correction.