A Bunion is an enlargement and displacement of the joint of the big toe. It is often associated with the big toe moving towards the smaller toes. Sometimes the big toes can move so far that it crowds the smaller toes, and often the second to will overlap the big toe. This is caused by a biomechanical problem in the foot. There is a muscle in the lower leg called the peroneus longus. It runs along the outside of the lower leg, goes under the ankle bone on the outside, then it runs under the arch of the foot, and attaches at the base of the First Metatarsal. When this muscle fires or contracts it pulls on this Metatarsal bone to keep it held in place. As the foot flattens out more than it should the angle that this muscle pulls is changed, and it becomes less effective. The Metatarsal bone will move out from the pressure, and the toe will begin to buckle due to the forces.
Orthotics will never correct the Bunion if it has already formed. They can help the bunion from getting any worse, and they can also prevent the problem from occurring by balancing up the foot biomechanically. This will return the pull of this muscle to normal angle, thus preventing the big toe from drifting.