If there is too much pressure on the inside of the foot at the base of the big toe, the big toe is forced towards the other toes. A hard, bony lump forms on the joint, causing pain, inflammation and swelling.

A bunion is a deformity of the big toe. The toe tilts towards the smaller toes and a bony lump appears on the inside of the foot, at the end of the 'knuckle bone' of the big toe. Sometimes a soft fluid swelling develops over the bony lump. The first metatarsal bone that runs along the foot to the big toe can also be pushed out of alignment, causing instability and difficulty walking.

Bunions are more common in women than in men. They can be the result of wearing shoes that are too tight. Women's ligaments are also looser and less likely to keep the big toe properly aligned. The condition can also be hereditary.

If bunions develop later in life, there is a possibility that the bone deformity is caused by arthritis.