[Pathogenesis of hallux valgus].

In terms of its etiology, the hallux valgus deformity is differentiated into a primary and a secondary form. Widening of the angle between the first and second metatarsals (metatarsus primus varus) is often associated with a hallux valgus deformity (primary hallux valgus). Secondary hallux valgus is caused by changes to the hind- and midfoot. In the presence of a pes planovalgus, lowering of the navicular and talus bones results in a deformation of the hindfoot. This leads to the collapse of the longitudinal arch and pronation of the forefoot (splay-foot). As a result all the tendons that cross the first metatarsophalangeal joint now function as adductors, and promote the further development of hallux valgus.