Corpus3D

Wrist and hand

Trapezium

Os trapezium

How to find it
Follow the first metacarpal proximally until you feel a joint line. Move the thumb back and forth: the line opens and closes, and the bone directly proximal to it is the one you want.
What you use it for
With the base of the first metacarpal it forms the saddle joint of the thumb. Osteoarthritis of it, thumb base arthritis, is one of the commonest hand complaints after fifty.
On the bone
Trapezium
Body region
Wrist and hand