Wrist

What it is

The joint between the lower end of the radius and the first row of carpal bones — the scaphoid, lunate and triquetrum.

The detail that surprises people: the ulna does not reach the wrist joint. It is separated from the carpal bones by the triangular fibrocartilage complex, a disc of cartilage and ligament that both cushions that side and binds the two forearm bones together. So the hand hangs off one forearm bone, not two — which is exactly what allows the radius to rotate freely in pronation and supination while the hand comes with it.

What people call "the wrist" is really this joint plus the midcarpal joint below it and the many small intercarpal joints, all contributing to the overall movement.

What it does

Flexion, extension, and deviation towards the thumb or little finger. Combining these gives circumduction. It does not rotate — turning the palm over happens in the forearm.

Extension and ulnar deviation have more range than flexion and radial deviation.

The wrist is held in slight extension during forceful gripping, because the finger flexors would otherwise bend it. Grip is markedly weaker with a flexed wrist.

What loads it

Anything gripped or carried. Any pressing position taking weight through the hand — push-ups, and front-rack positions — loads it in extension.

What is commonly got wrong about it

"Wrist rotation" exercises. The wrist does not rotate. Turning the hand over is forearm rotation.

Carpal tunnel syndrome and keyboards. The association is much weaker in the evidence than the popular account suggests. It is nerve compression, and hand numbness needs assessment rather than a wrist brace bought on the strength of a search result.

That wrist pain in pressing means poor mobility. It might mean that, or it might mean several other things. The scaphoid in particular is a bone with a poor blood supply where a missed fracture has real consequences, which is a reason to take persistent wrist pain after a fall seriously.