A bunion typically appears as a bony bump on the inside edge of the foot, where the innermost long bone of the foot (called the first metatarsal) meets the base of the big toe.
The visible bump appears when the first metatarsal tilts outward causing the tip (or head) of the bone to protrude on the inside of the foot near the big toe joint. When a bunion develops on the base of the little toe, it is known as a tailor's bunion.
Causes of a bunion can include genetics, structural abnormalities of the foot, pregnancy, rheumatoid arthritis and long-term wearing of high heels or pointy shoes.