Capitate
Os capitatum
Also known as: os magnum
The largest carpal bone, in the centre of the distal row, whose rounded head articulates with the scaphoid and lunate. It is the first carpal to ossify.
Overview
The capitate has a rounded head that sits in the concavity formed by the scaphoid and lunate — the centre of rotation of the wrist — a neck and a body whose distal surface articulates mainly with the 3rd metacarpal (and partly the 2nd and 4th). Laterally it meets the trapezoid and medially the hamate. With the 3rd metacarpal it forms the central longitudinal axis of the hand, transmitting much of the load of a clenched fist. Its proximal pole, like that of the scaphoid, has a retrograde blood supply, so rare fractures of the neck (e.g. in scaphocapitate syndrome) may lead to avascular necrosis.
- Location
Centre of the distal carpal row.
Anatomy
- Articulations
Scaphoid, lunate, trapezoid, hamate and metacarpals 2–4.
- Ossification
First carpal to ossify, ≈1–3 months after birth.
Function
- Central keystone of the carpus and axis of wrist movement
- Transmits load from the 3rd metacarpal to the lunate and radius
Compiled from standard anatomy and physiology references — see the Skeletal System sources. For education only; not medical advice.