There are many causes of bunion, the common ones are heredity, bad shoe-wearing habit, rheumatoid arthritis and so on. 1. Heredity: Heredity and other congenital factors, such as flat feet, can cause muscle tension imbalance, leading to instability of the first metatarsophalangeal joint, which ultimately causes bunion. 2. Bad footwear habits: If you wear high-heeled shoes, the front part of your foot will be squeezed into a narrow space, and in the long run, the hard surface of the shoe will force you to bunionize your toes. 3. Rheumatoid arthritis: mainly characterized by aggressive arthritis, with morning stiffness, swelling and pain in the joints in the early stages of the disease, and later developing into joint deformities leading to bunions. There may be other reasons for bunion, such as neuromuscular lesions, etc. It is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, and standardize the treatment under the guidance of the doctor.