Multiple factors have been implicated in the etiology of hallux valgus. This perspective suggests that collapse of the arch under weight-bearing load orients the first metatarsal axis toward vertical and predisposes adduction of the first metatarsal, which initiates deformity. This grounded theory was built upon the following points:
The first metatarsal rotates about its own axis.
Orientation of this axis is variable and dependent upon the shape of the medial arch.
The arch is best able to carry weight and keep its shape when the first metatarsal is properly aligned.
Collapse of the arch tends to orient the first metatarsal axis towards vertical.
Adduction of the first metatarsal occurs about a vertical axis.
Adduction of the first metatarsal predisposes hallux valgus.