Muscle Test Group: Pronator teres and pronator quadratus.
• Pronates the forearm at the wrist.
• Technically tested as a group, the pronator teres is primarily tested as its function obscures the fine function of the pronator quadratus.
Muscle Function: Pronates the forearm.
Palpation: Too deep to palpate.
Strength Testing: Position – the elbow in full flexion (end-range) to put the humeral head of the pronator teres at a disadvantage. Stabilize – the elbow to avoid shoulder abduction. Resist – against pronation of the forearm, proximal to the wrist and on forearm, in the direction of supination.
Possible Substitutions: Pronator teres (bending the elbow can reduce this effect by preventing the long head from being effective; however, you can’t completely eliminate the function of the pronator teres from the exam). In fact, patients that have had distal anterior interosseous nerve transfers to the ulnar nerve can still fully pronate with the above strength testing maneuver.
• Roots: C8, T1.
• Nerve: Median nerve, anterior interosseous nerve.
• Innervation Route: C8, T1 → median nerve → anterior interosseous nerve → pronator quadratus branch.
Origins: Anterior surface of distal ¼ of ulna, medial aspect; oblique ridge.
Insertion: Anterior surface of distal ¼ of radius, lateral aspect.