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Pronator Teres (PT)

OVERVIEW
Muscle Test Group:
Pronator teres and pronator quadratus.
 
Key Points:
• Pronation is often overlooked when injured, but it is a critical function for positioning the arm and doing certain activities (turning a key, etc).
• Technically tested as a group, the pronator teres is primarily tested as its function obscures the fine function of the pronator quadratus.

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EXAMINATION
Muscle Function:
Pronation of the forearm.  Pronator teres also assists in flexion of the elbow joint.
 
Palpation: Pronator teres can be palpated distal to the antecubital space on the lateral side of the forearm. Fingers may be placed into the cubital fossa during pronation.  (Note that in contrast pronator quadratus is too deep to be palpated.)
 
Strength Testing: Position – the subject in seated with elbow flexed to 90º, arm at the side, and forearm in supination to end-range. Stabilization – the forearm and with the wrist in neutral position. Resist – against pronation of the forearm at the distal forearm in the direction of supination.  Or, place the patient’s forearm in pronation and instruct them not to move from that position and then the examiner tries to supinate the forearm.
 
Pronator Quadratus – Theoretically, bending the elbow while asking the patient to pronate is thought to specifically test the pronator quadratus function by eliminating pronator teres function.  However, this is a moot point because patients who have had the pronator quadratus denervated (by anterior interosseous nerve branch transfer or other means) will still be able to pronate even with the elbow flexed.
 
Possible Substitutions: Pronator quadratus. Muscles for wrist flexors and shoulder medial rotations. To eliminate the medial rotator’s contribution, stabilize the humerus against the trunk during testing. 
 
Relevant Anatomy:
Pronator Teres
Innervation:
• Roots: C6, C7.
• Nerve: Median nerve.
• Innervation Route: C6, C7 → median nerve → pronator teres branch.
Origins of Humeral Head: Proximal to the medial epicondyle of humerus, common flexor tendon, and deep antebrachial fascia.
 
Origin of Ulnar Head: Medial side of coronoid process of ulna.
 
Insertion: Middle of lateral surface of radius.
 
Pronator Quadratus
Innervation:
• Roots: C8, T1.
• Nerve: Median nerve, anterior interosseous nerve.
• Innervation Route:  C8, T1 → median nerve → anterior interosseous nerve → pronator quadrates branch.
Origins: Anterior surface of distal ¼ of ulna, medial aspect; oblique ridge.
 
Insertion: Anterior surface of distal ¼ of radius, lateral aspect.