A bunion is a thickened lump at the base of the big toe. The underlying cause is a minor bone deformity, called hallux valgus, in which the joint at the base of the big toe projects outward, forcing the toe to turn inward. Pressure on the projecting bone causes the surrounding tissues to thicken, forming a bunion. A bunion may be painful and may become inflamed and callused.
Small bunions may be remedied by using a bunion splint to straighten the big toe. For a large or troublesome bunion, surgery to remove the protruding area of bone and straighten the big toe may be recommended.