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| Latin | Musculus supinator |
|---|---|
| Origin |
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| Insertion |
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| Action |
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| Nerve | Deep branch of the radial nerve (posterior interosseous nerve) (C5–C6) |
| Name | Latin supinare, 'to lay on the back' — it turns the palm up. |
Palpation
- Client supine, forearm resting in mid-position (thumb up) and wrist relaxed.
- Find the lateral epicondyle, then move just below it onto the upper back-and-outer part of the forearm, over the neck of the radius.
- Keep the wrist passive so the overlying wrist extensors stay soft, and press gently through them towards the radius.
- Ask the client to turn the palm up against light resistance with the elbow straight, so biceps brachii does less of the work. Supinator lies deep, so the contraction feels faint.
Supinator sits under the wrist extensors just below the Lateral epicondyle of humerus, so tenderness here is easily mistaken for the extensor tendons. To tell them apart, compare resisted supination (supinator) with resisted wrist extension (the Wrist extensors). Work it with slow, sustained Compression through relaxed extensors rather than deep friction.
The deep branch of the radial nerve passes through the belly of supinator in most people (Wikipedia says about 70%). If pressure here brings on tingling or weakness in the back of the forearm or hand, stop and suggest the client sees a health professional.
Wikipedia gives mainly C6 with some C5 (and possibly C7) input; Gray’s (1918) gives C6 alone.