Bunions are an organised sack of fluid lying under the skin and over or around the big toe joint. They form as a result of deep shear and friction (rubbing) over bony prominences around the 1st metatarsal bone that help form the big toe joint. Most commonly they form after the development of hallux valgus deformity (often incorrectly called a ‘bunion) or arthritis within the big toe joint. Both conditions cause enlargement of the bone supplying the joint and the rubbing that forms the bunion usually develops because shoes no longer fit correctly.