Bunions. X-ray of a section through the feet of an 82-year-old patient with bunions affected both big toes. A bunion (hallux vulgas) is a swelling of the joint between the big toe and the first metatarsal bone. It causes the base of the big toe to project outwards and the tip of it to point inwards. Bunions are caused by the rubbing of ill-fitting shoes. The deformity can be corrected surgically. Here, it has almost caused total dislocation of the big toe joint.