Upper limb
Opponens Pollicis
Musculus opponens pollicis
- Origin
- Trapezium bone and flexor retinaculum
- Insertion
- Lateral border of the first metacarpal bone
- Function
- Opposes the thumb toward the other fingers (basis of the pincer and cylindrical grip)
- Innervation
- Median nerve (recurrent/thenar branch), C8–T1
- Movement & chain
- The primary muscle for thumb opposition; together with abductor pollicis brevis and flexor pollicis brevis, it forms the thenar musculature.
- Palpation
- Deep beneath abductor pollicis brevis in the thenar eminence, palpable as resistance during active opposition of the thumb toward the little finger.
- Clinical
- In carpal tunnel syndrome or a median nerve lesion, opposition weakness (a positive tendency toward 'ape hand') is a key symptom of thenar atrophy.
- Segmental innervation
- Median nerve, C8–T1.
- In clinical practice
- The thumb-to-little-finger opposition test is a standard clinical screen for the motor function of the median nerve.
- Region in the model
- Upper limb