| Third metatarsal bone | |
| Latin: | os metatarsale III |
The third metatarsal bone is a long bone in the foot. It is the second longest metatarsal, the longest being the second metatarsal. The third metatarsal is analogous to the third metacarpal bone in the hand[1]
Like the four other metatarsal bones, it can be divided into three part: base, body and head. The base is the part closest to the ankle and the head is closest to the toes. The narrowed part in the middle is referred to as the body of the bone. The bone is somewhat flattened, giving it two surfaces: the plantar (towards the sole of the foot) and the dorsal side (the area facing upwards while standing).[1] These surfaces are rough for the attachment of ligaments. The bone is curved longitudinally, so as to be concave below, and slightly convex above.
The base or posterior extremity is wedge-shaped.[1] The third metatarsal bone articulates proximally, by means of a triangular smooth surface, with the third cuneiform; medially, by two facets, with the second metatarsal; and laterally, by a single facet, with the fourth metatarsal. This last facet is situated at the dorsal angle of the base.
The head or anterior extremity articulates with the third proximal phalanx.
The first Plantar interossei muscle originates from the medial side of the base and shaft of the third metatarsal. The function of the muscle is to move the third toe medially and move the toes together.[2]
The horizontal head of the adductor hallucis also originates from the lateral side of the metacarpophalangeal joint and from the deep transverse metatarsal ligament,[2] a narrow band which runs across and connects together the heads of all the metatarsal bones.
| Muscle | Direction | Attachment[3] |
|---|---|---|
| Origin | Medial side of the shaft | |
| Origin | Lateral side of the shaft | |
| Origin | Medial side of the base and shaft | |
| Origin | Deep transverse metatarsal ligament and the metacarpophalangeal joint | |