Pronator teres
The upper of the two muscles that turn your palm downward, with the median nerve running between its heads.
- Type
- Muscle
- Region
- Forearm
- Standard name
- m. pronator teres
- Origin
- Medial epicondyle of the humerus (humeral head) and the coronoid process of the ulna (ulnar head)
- Insertion
- Lateral surface of the middle of the radius
- Actions
- forearm pronationelbow flexion
- Verify
- TA2 2478 TA98 A04.6.02.025
What it is
A short muscle running diagonally across the upper forearm, from the inner bump of the elbow down and outward to the middle of the radius. It forms the inner border of the cubital fossa, the triangular hollow in front of your elbow.
It has two heads, and the median nerve passes between them — a clinically important relationship and a standard dissection landmark.
What it does
Pronates the forearm — turns the palm downward — by pulling on the radius so it crosses over the ulna. It assists weakly in elbow flexion.
Pronation and supination happen because the radius rotates around the fixed ulna. Every muscle that pronates or supinates does so by attaching to the radius and spinning it.
What loads it
Resisted pronation, and gripping with the palm downward. Any activity involving repeated turning of the hand palm-down under load.
What is commonly got wrong about it
That pronation is done at the wrist. It happens between the two forearm bones, at the radio-ulnar joints, above and below. The wrist joint itself does not rotate.
"Golfer's elbow" as one structure. Pain at the inner elbow involves the common flexor tendon, where this muscle and several others originate together. Which structure is involved in an individual case is a clinical question.
That pronator teres does most of the pronating. Pronator quadratus at the wrist is the primary pronator for unresisted movement; this one is recruited more as speed and resistance rise.