Opponens pollicis flexes and medially rotates the first metacarpal to oppose the thumb.
The opponens pollicis is a deep, intrinsic muscle of the hand located in the thenar compartment. It is responsible for opposition of the thumb — the unique movement that brings the thumb across the palm to touch the tips of the other fingers. This muscle plays a critical role in human hand function, enabling gripping, pinching, and fine motor skills.
The opponens pollicis lies deep to the abductor pollicis brevis and lateral to the flexor pollicis brevis in the thenar eminence. It spans from the flexor retinaculum and trapezium to the shaft of the first metacarpal bone.
The muscle is small, triangular, and lies obliquely across the thenar region.
The opponens pollicis enables:
Innervated by the recurrent branch of the median nerve (C8–T1).
In some cases, the deep branch of the ulnar nerve may contribute (dual innervation), especially if the median nerve is compromised.
The opponens pollicis lies deep to the abductor pollicis brevis. It is medial to the flexor pollicis brevis and lateral to the first metacarpal. The radial artery passes lateral to it before contributing to the deep palmar arch.
Although not directly visible, the bulk of the opponens pollicis contributes to the shape of the thenar eminence. Its activity can be inferred by observing thumb rotation and cupping of the palm during opposition.
The opponens pollicis arises from the preaxial (anterior) muscle mass of the hand during embryonic development. Its function and innervation by the median nerve reflect its role in the evolution of the opposable thumb.
In many non-human primates, the opponens pollicis is underdeveloped or absent, corresponding to limited thumb opposition. In humans, its advanced development is crucial for the dexterous use of tools and objects — a hallmark of manual skill.