The primary cause of bunions is prolonged stress on the joints, which is often associated with wearing poorly fitting shoes. This includes shoes that are narrow in the toes, such as many kinds of high heels. Because of this, bunions more commonly develop in women. However, there are other risk factors, including genetics and arthritis, that can lead to their development.
If you are concerned about developing a deformity such as bunions, there are preventative measures you can take, such as switching to a more comfortable shoe.