|First metatarsal bone|
|Latin||Os metatarsale I|
|Anatomical terms of bone|
Like the four other metatarsals, it can be divided into three parts: base, body and head. The base is the part closest to the ankle and the head is closest to the big toe. The narrowed part in the middle is referred to as the body of the bone. The bone is somewhat flattened, giving it two sides: the plantar (towards the sole of the foot) and the dorsal side (the area facing upwards while standing).
The base presents, as a rule, no articular facets (joint surfaces) on its sides, but occasionally on the lateral side there is an oval facet, by which it articulates with the second metatarsal. On the lateral part of the plantar surface there is a rough oval prominence, or tuberosity, for the insertion of the tendon of the fibularis longus.
The first metatarsal articulates (forms joints) with the medial cuneiform and to a small extent with the intermediate cuneiform bone. Its proximal articular surface is large and kidney-shaped; its circumference is grooved, for the tarsometatarsal ligaments, and medially gives insertion to part of the tendon of the tibialis anterior.
The body of the bone is strong, and of well-marked prismoid form.
The head is large; on its plantar surface are two grooved facets on which the sesamoid bones glide; the facets are separated by a smooth elevation.
The tibialis anterior inserts at the basis of the bone, while the fibularis longus inserts at the tuberosity. The lateral part of the first dorsal interosseus muscle originates from the medial side of the bone. Its function is to spread the toes.
|Tibialis anterior||Insertion||Basis of first metatarsal|
|Fibularis longus||Insertion||Tuberosity of first metatarsal|
|Dorsal interossei I||Origin||Lateral part of first metatarsal|
Sesamoid bones at the distal end of the first metatarsal.