The thenar eminence is formed by four intrinsic thumb muscles whose coordinated action produces thumb opposition — the defining human hand movement.
| Origin | Flexor retinaculum, trapezium, first metacarpal base (collectively) |
|---|---|
| Insertion | Base of proximal phalanx of thumb, first metacarpal, extensor expansion (collectively) |
| Nerve Supply | Recurrent (thenar) branch of median nerve (C8, T1) for APB, superficial FPB, OP; Deep ulnar nerve (C8, T1) for AdP and deep FPB |
| Blood Supply | Radial artery superficial palmar branch; Princeps pollicis artery |
| Actions | Thumb abduction (APB); Thumb opposition (OP); Thumb MCP flexion (FPB); Thumb adduction (AdP) |
|---|
Thenar wasting from median nerve CTS is detected by flattening of the radial palmar eminence. APB is the specific muscle tested in recurrent branch territory. Complete thenar wasting requires all four muscles to be assessed to distinguish CTS from combined palsy.
The rounded radial palmar mass — prominent during thumb abduction and opposition.
Irreversible thenar atrophy from chronic median nerve compression requiring urgent decompression.
