A bunion is a bony deformity of the joint at the base of the big toe. This joint is known as the metatarsophalangeal (MTP) joint. The medical name for a bunion is hallux valgus.
Structure of the foot
The foot is divided into three parts:
- the hindfoot
- the midfoot
- the forefoot
The forefoot (front part of the foot) is made up of five bones called the metatarsals. These join the midfoot to the bones inside the toes. The big toe is usually in line with the first metatarsal, the second toe is in line with the second metatarsal and this pattern of alignment continues for each metatarsal and toe.
Sometimes, the big toe can become angled outwards towards the middle of the foot and second toe. This forces the top of the first metatarsal to stick out from the side of the foot at the base of the big toe. If this happens, the bones can become misaligned and a painful bunion can form.
It is not known exactly what causes bunions, but wearing badly fitting shoes is thought to make the condition worse.
Research also suggests that bunions may run in families. It is thought that bunions are more likely to occur in people who have unusually flexible joints, and that this flexibility may be inherited.
In some cases, certain health conditions, such as rheumatoid arthritis and gout, may also be responsible for the formation of bunions. These conditions cause pain and inflammation in the joints. See Bunion – causes for more information.
Who is affected by bunions?
Anyone can develop a bunion, but they are usually more common in women than men. This may simply be because of the style of footwear that women wear.
A range of treatments is available for bunions, including:
- modifying footwear
- orthotics, such as insoles, bunion pads and toe spacers
Surgery may be considered if a person’s symptoms are severe and do not respond to non-surgical treatment. The type of surgery used will depend on the level of deformity, the severity of any other associated symptoms, the patient’s age and any other associated medical conditions.
Bunion surgery is usually effective, with up to 85% of cases resulting in improvement to symptoms. However, the deformity can sometimes return after bunion surgery.
See Bunion – treatment for more information about the range of available treatments.