this perspective article gives a response to this challenge wherein the first metatarsal axis and its predisposition to hallux valgus are described. The literature and theory are predicated upon 3 major tenets:(1) the first metatarsal rotates about its own axis; (2) collapse of the arch orients (tilts) of the first metatarsal axis toward vertical, which allows the first metatarsal to adduct with less anatomical resistance; and (3) instability of the first metatarsal arch segment is a related factor of hallux valgus. These tenets of first metatarsal biomechanics support our theory for hallux valgus that collapse of the arch with vertical orientation of the first metatarsal axis initiates deformity. Part 2 concludes with a discussion using this theoretical perspective to advocate for orthosesbased treatment strategies.