"Hypermobiity of the first metatarsal bone" is due to unusually free motion in the joint between the inner cuneiform and scaphoid bones, and between the inner and middle cuneiforms.
The resulting instability of the inner anterior pillar affects the metatarsal portion, and also the longitudinal arch of the foot.
Physiological hypertrophy of the second metatarsal bone is the most notable structural feature. It is similar to the enlargement of this bone observed in feet with a short first metatarsal.
Metatarsalgic symptoms are more frequent than the symptoms of arch strain, although pain may coexist both in the forepart of the foot and in the arch.
Subjective symptoms rarely appear before adult life, although the laxity of the first metatarsal bone seems to be a condition acquired congenitally or during early childhood.
Analysis of a large group of metatarsalgic cases in which hypermobility or brevity of the first metatarsal was present (singly or in combination), indicates that the disorder is essentially a physiological one, comprising an improper distribution of stresses borne by the different metatarsal bones; it is not attended with any measurable change in the relative position of the metatarsal heads as inferred by the term "depressed anterior arches". This term is therefore regarded as inapt, and as conducive to misapprehension of the real nature of static disorders in this part of the foot.