Big toe after bunion surgery. Coloured X-ray showing a corrected bunion on the foot of a 46 year old woman, showing the big toe pinned at a joint. A metal plate (green) has been screwed into the metatarsal bone and adjacent phalanges bone of the big toe to straighten and immobilize it. A bunion is a swelling of this joint of the big toe (hallux). Deformation of this joint is called hallux valgus in which the joint at the base of the big toe projects outwards while the tip of the toe turns inwards. Severe cases may lead to the formation of a bursa, a sac of fibrous tissue which was removed here. A bony outgrowth of the metatarsal is still seen. Bunions are often caused by the wearing of ill-fitting shoes. A plaster cast has been placed around the foot.