The pronator teres is the primary pronator of the forearm, a two-headed muscle whose humeral and ulnar heads sandwich the median nerve between them as it passes from the arm into the forearm. This anatomical relationship makes it the key structure in pronator syndrome, where the median nerve is compressed between the heads and produces symptoms that closely resemble carpal tunnel syndrome but originate at the elbow.
| Origin | Medial epicondyle via the common flexor origin; Medial surface of the coronoid process of the ulna |
|---|---|
| Insertion | Middle third of the lateral radius at its maximum convexity |
| Nerve Supply | Median nerve (C6, C7), which passes between the two heads of the muscle |
| Blood Supply | Ulnar artery |
| Actions | Pronation of the forearm; Weak assistance in elbow flexion |
|---|
It rotates the forearm palm-down through a combination of radial rotation and is most active during powerful or rapid pronation movements such as using a screwdriver or throwing a pitch.
Pronator syndrome produces anterior forearm aching and hand paraesthesia that is reproduced by resisted forearm pronation with the elbow extended. The key clinical distinction from carpal tunnel syndrome is the absence of nocturnal symptoms and the presence of palm paraesthesia, which is innervated by the palmar cutaneous branch of the median nerve that branches proximal to the carpal tunnel. Tenderness in the proximal forearm over the muscle belly is a reliable clinical sign.
The pronator teres is palpable as an oblique cord crossing the proximal forearm from the medial epicondyle toward the mid-radius, becoming clearly firm during resisted forearm pronation with the elbow extended.
Median nerve entrapment between the two heads of pronator teres producing forearm aching and hand paraesthesia reproduced by resisted pronation with elbow extension, distinguished from carpal tunnel syndrome by proximal forearm tenderness and palm sensory involvement.
Muscle fibre tears from repetitive forceful pronation under load, producing medial forearm pain that worsens with resisted pronation and is common in racket sport players and manual workers.
