Bunions begin when your big toe starts to point toward your smaller toes.
Once the big toe moves out of its normal position, its tendons can actually pull the toe even farther out of alignment. This is why bunions often continue to get worse without surgery.
As the big toe bends toward the smaller toes, this stretches the joint capsule or ligaments of the MTP joint. In this position, one side of the joint capsule and ligaments are stretched, while the other side shortens. When this happens, the end of the first metatarsal becomes prominent or sticks out on the inside of your foot, causing a bunion. As you can see, a bunion is not a bump that grows at the end of your bone, it is formed because the bones are actually crooked.
There are many reasons why this might happen. For example, you might wear shoes with a narrow toe box that bends your big toe in this direction, or you may have flat feet, arthritis, previous foot injuries or weak ligaments.