Bone
Trapezium
Wrist bone supporting the thumb base
High-yield
The thumb CMC joint is the articulation between trapezium and first metacarpal. The similarly named trapezoid sits just medial to the trapezium and chiefly supports the index metacarpal.
Overview
At the radial end of the distal carpal row, the trapezium supports the first metacarpal on a saddle-shaped surface. This joint's shape and its soft-tissue control help the thumb turn across the palm for opposition.
Reference facts
- Bone type
- A short bone in the distal carpal row
- Key landmarks
- Palmar tubercle or ridge; saddle-shaped surface facing the thumb metacarpal
- Articulations
- First metacarpal distally; scaphoid proximally; trapezoid and second metacarpal medially
Mnemonic
Read from the thumb side in both rows: proximal S-L-T-P; distal T-T-C-H. Expand each letter into the bone's name as you picture the two rows.
Clinical correlation
Osteoarthritis at the thumb base can cause pain with pinch and grip. Imaging changes and symptoms do not always match: some people have visible joint wear with little or no pain.
Frequently asked questions
What type of bone is the trapezium?
A short bone in the distal carpal row.
What does the trapezium articulate with?
First metacarpal distally; scaphoid proximally; trapezoid and second metacarpal medially.
What are the key landmarks of the trapezium?
Palmar tubercle or ridge; saddle-shaped surface facing the thumb metacarpal.