Bunions (cont.)

While the precise cause is not known, there seem to be inherited (genetic) factors that lead to abnormal foot function like overpronation that can predispose to the development of bunions. This is especially common when bunions occur in younger individuals. This abnormal biomechanics can lead to instability of the metatarsal phalangeal joint and muscle imbalance resulting in the deformity.

Although shoe gear doesn't directly cause a bunion, it can certainly make the bunion painful and swollen. Other less common causes of bunion deformities include trauma (sprains, fractures, and nerve injuries), neuromuscular disorders (polio or Charcot-Marie-Tooth disease) and limb-length discrepancies (one leg shorter than the other) where the longer leg develops the bunion.

Bunions most commonly affect women. Some studies report that bunion symptoms occur nearly 10 times more frequently in women. It has been suggested that tight-fitting shoes, especially high-heel and narrow-toed shoes, might increase the risk for bunion formation. Tight footwear certainly is a factor in precipitating the pain and swelling of bunions. Complaints of bunions are reported to be more prevalent in people who wear shoes than in barefoot people.

Other risk factors for the development of bunions include abnormal formation of the bones of the foot at birth (congenital) and arthritic diseases such as rheumatoid arthritis. In some cases, repetitive stresses to the foot can lead to bunion formation. Bunions are common in ballet dancers.

Source: MedicineNet.com
http://www.medicinenet.com/bunions/article.htm