The capitate (os magnum) is the largest of the carpal bones in the hand. It lies at the centre of the distal row, articulating with the trapezoid laterally and the hamate medially. It also articulates with the lunate and scaphoid proximally, and with the index, middle and ring metacarpals distally.
The capitate (lesser multangular refers to the trapezoid, navicular to the scaphoid, and 2nd, 3rd and 4th metacarpals to the index, middle and ring metacarpals respectively)
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The capitate can be felt by identifying the middle metacarpal and then sliding proximally until reaching a slight depression. This is the location of the capitate, which becomes more prominent on flexion of the wrist.
The capitate has a head which projects proximally into the gap between scaphoid and lunate, the proximal surface of the head articulating with the lunate and the lateral surface articulating with the scaphoid. The facet for trapezoid is usually continuous with that for scaphoid. The medial surface bears a large facet for the hamate. There are rough areas on the palmar surface and dorsal surface. The capitate is often described as having a neck where it constricts centrally and a body as the distal portion.
- A dorsal ligament attaches to the dorsal surface
- A palmar ligament attaches to the palmar surface
- Interosseous ligaments link capitate to hamate and usually to trapezoid (although this may be absent)
- Articulates with the scaphoid at the midcarpal joint
- Articulates with the lunate at the midcarpal joint
- Articulates with the trapezoid at an intercarpal joint
- Articulates with the hamate at an intercarpal joint
- Articulates with the index metacarpal at the carpometacarpal joint
- Articulates with the middle metacarpal at the carpometacarpal joint
- Articulates with the ring metacarpal at the carpometacarpal joint
The capitate begins to ossify in the second month.
- May fracture.