Dr. Ebraheim’s educational animated video describes the anatomy of the Supinator muscle.
Which muscles supinate the forearm?
1- Supinator muscle (radial nerve). 2- Biceps muscle (musculocutaneous nerve).
Which muscles pronate the forearm?
1- Pronator teres muscle (median nerve). 2- Pronator quadratus muscle (median nerve).
The function of the pronato teres is to pronate the forearm (along with the pronator quadratus) so that the palm turns posterior.
The function of the supinator muscle (along with the biceps muscle) is to supinate the forearm or rotate the radius to turn the palm anteriorly.
Elbow range of motion Pronation/Supination:
- Normal range of pronation/supination is between 80°-90°.
- Normal flexion of the elbow is between 0°- 150°.
- Functional range of motion is from 30°- 130° of flexion and 50° of pronation/supination.
The median nerve passes between the two heads of the pronator teres muscle; this may be an area of entrapment for the median nerve during forearm rotation.
The deep branch of the radial nerve passes through the supinator muscle, at this area the nerve can become entrapped.
Origin and Insertion:
- The Supinator muscle:
• Origin: is from the lateral epicondyle of the humerus, supinator crest of ulna, the radial collateral ligament, and the annular ligament.
• The supinator muscle curves around the upper third of the radius.
• Insertion: it inserts into the lateral, posterior, and anterior surface of the proximal 1/3 of the radius.
• Innervation: the supinator muscle is a broad muscle in the posterior compartment of the forearm supplied by the posterior interosseous nerve, which is a continuation of the deep branch of the radial nerve (C5, C6).
• The radial nerve divides into deep and sensory branches just proximal to the supinator muscle.
• The posterior interosseous nerve (deep) gives a branch to the supinator muscle just before it enters the muscle; the posterior interosseous nerve (deep) enters the extensor compartment of the forearm through the supinator muscle.
• The area in which the posterior interosseous nerve passes through is called the “Arcade of Frohse” and this area is often a site for entrapment of the posterior interosseous nerve.
• The posterior interosseous nerve does not supply cutaneous sensation and is purely a motor nerve.
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Background music provided as a free download from YouTube Audio Library.
Song Title: Every Step
