Muscle · Hand

Opponens pollicis

Musculus opponens pollicis

The deepest of the three thenar muscles, and the one that makes the human hand what it is. Rather than moving the thumb's knuckles, it rotates the whole first metacarpal inward and draws it across the palm, turning the thumb pad to face the fingertips. That single rotation is what allows a pinch, a pen grip, a key turn, or a button — the precision half of grip. It lies hidden beneath abductor pollicis brevis, and like its neighbours it depends on the median nerve.