Thumb
The carpometacarpal joint of the thumb, also known as the first carpometacarpal joint, or the trapeziometacarpal joint (TMC) because it connects the trapezium to the first metacarpal bone, plays an irreplaceable role in the normal functioning of the thumb. The most important joint connecting the wrist to the metacarpus, osteoarthritis of the TMC is a severely disabling condition; up to twenty times more common among old women than in average.
Pronation-supination of the first metacarpal is especially important for the action of opposition. The movements of the first CMC is limited by the shape of the joint, by the capsulo-ligamentous complex surrounding the joint, and by the balance among involved muscles. If the first metacarpal fails to sit well 'on the saddle', for example because of hypoplasia, the first CMC joint tends to be subluxated (i.e. slightly displaced) towards the radius.
The capsule is sufficiently slack to allow a wide range of movements and a distraction of roughly 3 mm, while reinforcing ligaments and tendons give stability to the joint. It is slightly thicker on its dorsal side than on the other.
The first carpometacarpal joint is a frequent site of osteoarthritis in postmenopausal women.
Read more about this topic: Carpometacarpal Joint
Famous quotes containing the word thumb:
“I had a consuming ambition to possess a miller’s thumb. I believe I have never since wanted anything more desperately than I wanted my right thumb to be flattened as my father’s had become, during his earlier years of a miller’s life.”
—Jane Addams (1860–1935)
“Your small hands, precisely equal to my own—
only the thumb is larger, longer—in these hands
I could trust the world, or in many hands like these,
handling power-tools or steering-wheel
or touching a human face ...”
—Adrienne Rich (b. 1929)
“Give a lift to a tomato, you expect her to be nice, don’t ya? After all, what kind of dames thumb rides, Sunday school teachers?”
—Martin Goldsmith, and Edgar G. Ulmer. Charles Haskell, Jr. (Edmund MacDonald)