The opponens pollicis is the thenar muscle that produces the defining human function of precision pinch through thumb opposition. It rotates the first metacarpal into pronation at the CMC joint, aligning the thumb pad with the fingertips. Median nerve palsy (carpal tunnel syndrome, high median palsy) paralyses the opponens, eliminating opposition and producing the flat ape hand appearance.
| Origin | Flexor retinaculum and trapezium crest |
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| Insertion | Entire radial shaft and border of the first metacarpal — wraps around to produce CMC rotation |
| Nerve Supply | Recurrent (thenar) branch of the median nerve (C8, T1) |
| Blood Supply | Superficial palmar arch and princeps pollicis |
| Actions | First CMC joint opposition — combined palmarflexion and pronation of the thumb metacarpal that brings the thumb pad to face the finger pads; Deepens the palmar concavity during thumb opposition |
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The recurrent (thenar) branch of the median nerve supplies the opponens — it arises just distal to the transverse carpal ligament and curves radially into the thenar eminence. Carpal tunnel release must identify and protect this recurrent branch — damage produces permanent thenar weakness. The thenar branch can be extraligamentous (the safe zone), subligamentous (requiring careful release), or transligamentous (requiring the ligament to be cut through the nerve branch territory).
The opponens pollicis is the central thenar muscle, forming the bulk of the thenar eminence and becoming firm during resisted thumb opposition (touching the little finger tip).
Inadvertent thenar branch division during carpal tunnel release producing permanent opponens paralysis — prevented by identifying the branch before complete ligament division.
