The main cause is the fallen transverse arch, when the heads of the 2nd and 3rd metatarsals drop from the top of the arch to the base and these points become the source of excessive pressure. The foot rests on two instead of three points on the ground, making the foot unstable.
Hallux valgus is a medical term indicating that the first metatarsal has turned away from the midline of the body. Because the big toe is attached to a strong tendon, the toe is pulled inwards towards the midline of the body, making a V shape with the first metatarsal. There are painful fluid-filled sacs under the skin.
Orthotics are used to gradually realign the foot (after computer examination)