- There are eight carpal bones of the wrist, arranged in two rows of four.
- proximal row (radial to ulnar) : scaphoid, lunate, triquetrum, pisiform
- distal row (radial to ulnar) : trapezius, trapezoid, capitate, hamate
- The carpals articular with:
- the radius primarily, but also with the ulna proximally, forming the wrist joint (radiocarpal, ulnocarpal joints).
- the metacarpals distally, forming the carpometacarpal joints.
- Specifically, the joint between the trapezius and the metacarpal of the thumb is the 1st carpometacarpal joint, aka the famous saddle joint of the thumb.
- The walls of the carpal tunnel are formed by the tubercles of the scaphoid and trapezium laterally and the pisiform and the hook of the hamate medially.
NOTES:
- The piriform is a sesamoid (round) bone that formed later. That is why there are seven tarsal bones but eight carpal bones.
- There is a well-known mnemonic for learning the carpals: Some Lovers Try Positions That They Can’t Handle = Scaphoid, Lunate, Triquetrum, Pisiform, Trapezium, Trapezoid, Capitate, Hamate.
Anterior view of the wrist and hand on the right side of the body.
Posterior view of the wrist and hand on the right side of the body.
Anterior view of the carpals spaced out, on the right side of the body.
Posterior view of the carpals spaced out, on the right side of the body.
Proximal to distal view of the bones of the carpal tunnel on the right side of the body.
