Pronator quadratus
A small square muscle just above the wrist that is the primary pronator, despite pronator teres getting the name recognition.
- Type
- Muscle
- Region
- Forearm
- Standard name
- m. pronator quadratus
- Origin
- Distal quarter of the anterior surface of the ulna
- Insertion
- Distal quarter of the anterior surface of the radius
- Actions
- forearm pronation
- Verify
- TA2 2493 TA98 A04.6.02.038
What it is
A short, flat, four-sided muscle running straight across the front of the forearm just above the wrist, from ulna to radius. It is the deepest muscle of the front of the forearm.
Unlike the long muscles above it, it spans only the gap between the two bones.
What it does
Pronates the forearm, and is generally regarded as the primary pronator — the one initiating and performing unresisted pronation, with pronator teres joining as effort increases.
It also helps hold the two bones together at the wrist end, resisting them being pulled apart.
What loads it
Resisted pronation. Nothing loads it separately from pronator teres.
What is commonly got wrong about it
That pronator teres is the main pronator. Its name is better known and it is more accessible, but this is the muscle doing the routine work.
That it is unimportant because it is small. Its short fibres across a small gap are well suited to what it does. Force capacity depends on cross-section and leverage, not on length.