Inflamed bunion on a woman's foot. A bunion (hallux vulgas) is a swelling of the joint between the big toe and the first metatarsal bone (the bone in the sole beneath the big toe). 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. This bunion has become further inflamed (red area) by tight shoes. The deformity can be corrected surgically.