Experts continue to disagree on whether tight, high-heeled or too-narrow shoes cause bunions or whether footwear simply contributes to bunion development in a susceptible individual.
1 in 3 people will develop bunions at some stage in their lives. Bunions however are more common in women than men and become more common with age, particularly over the age of 45.
It is believed that the primary cause of bunions is usually genetic as certain foot types run in families. 7 out of 10 bunion patients will have a family history of bunion deformity and this can be passed through generations.
However if you are predisposed to bunions, high heels and tight fitting shoes will certainly accelerate the problem.
Bunions essentially develop because of a biomechanical imbalance and certain tendons and supportive structures of the first metatarsal are no longer functioning correctly. The pressures of bearing and shifting your weight can sometimes fall unevenly on the joints and tendons in your feet. This imbalance in pressure makes your big toe joint unstable, eventually moulding the parts of the joint into a hard knob that juts out beyond the normal shape of your foot. A variety of other conditions both extrinsic and intrinsic to the structure of the foot may cause this biomechanical abnormality.
Flat foot problems, arthritis and foot injuries as well as certain nerve conditions may also be responsible as they may cause abnormal weight distribution in the foot.
Bunions may also be associated with certain types of arthritis, particularly inflammatory types, such as rheumatoid arthritis. An occupation that puts extra stress on your feet or one that requires you to wear pointed shoes also can be a contributory cause.
Other general conditions play a part also, for example, joint laxity (hypermobility) is more common in the hallux valgus patient. Conditions such as Marfan’s and Ehlers-Danlos syndrome can produce remarkable joint laxity resulting in unstable and marked hallux valgus. This “splay foot” type is also seen in the more elderly patient where weak muscles within the feet (called intrinsic muscles) cause instability of the toes.
It is also known that hallux valgus occurs in unshod cultures although, in one study in Chinese Hong Kong, hallux valgus was 70 times more common among shoe-wearers compared with the unshod members of the same community.
Trauma to the foot can also be a causative factor as can nerve damage.
Many authorities believe that flatfoot also predisposes many patients to developing bunions
In summary the causes are often multifactorial; but listed as follows:
- Wearing improperly fitting shoes (particularly narrow and/or high-heeled shoes)
- Inherited condition
- Certain arthritic conditions and ligament disorders
- Age (the incidence of bunions increases with age)
- Being flatfooted with feet that roll inwards (over pronation)