There are 8 carpal bones that make up the wrist. The bones
are arranged in two rows: the
proximal bones
articulate
with the
distal ends of the
radius and
ulna (except for
the pisiform, which articulates only with the triquetrum and
attaches to the
ligaments of a few muscles of the hand and
arm); the distal bones articulate with the proximal ends of the
metacarpal bones.
Proximal row: The scaphoid gets its name
from its boat-like shape. It's on the radial side of the wrist.
Immediately medial to the scaphoid is the lunate
bone (previously known as the "semilunar" bone because its
concave shape resembles a half moon; the modern term
means "crescent-shaped"). Next is the triquetrum,
which is wedge-shaped (this three-sided bone was previously
known as "cuneiform", which means "wedge-shaped"; there
is a tarsal cuneiform bone as well and this may be the
reason for the change in the name). The most medial carpal
bone of the proximal row is the pisiform, so named
because it looks just like a pea.
Distal row: Starting on the radial side, the
trapezium is an irregular four-sided structure just as
its name implies. Medially is the trapezoid, also
four-sided but smaller than the trapezium. The
capitate, formerly called "os magnum" because it's
the largest of the carpal bones, has a head-like form as its
modern name would suggest. Finally, the hamate
bone is hook-shaped; "hamate" and "unciform" both mean
"having the shape of a hook", although "hamate" is the modern
term.
It is useful for radiologists, orthopedic surgeons, and any
other medical professional who might be involved in a
discussion of the bones of the wrist to know both the modern
and older versions of the names.
A mnemonic device for remembering the modern names
of the carpal bones:
"Some Lovers Try Positions
That They Can't
Handle."