ONIA: Posterior Forearm

Brachioradialis proximal attachment (origin)

Proximal two thirds of lateral supraepicondylar ridge of humerus

Brachioradialis distal attachment (insertion)

Lateral surface of distal end of radius proximal to styloid process

Brachioradialis nerve

Radial nerve (C5, C6, C7)

Brachioradialis action

Relatively weak flexion of forearm; maximal when forearm is in midpronated position

Extensor carpi radialis longus (ECRL) proximal attachment (origin)

Lateral supra-epicondylar ridge of humerus

Extensor carpi radialis longus (ECRL) distal attachment (insertion)

Dorsal aspect of base of 2nd metacarpal

Extensor carpi radialis longus (ECRL) nerve

Radial nerve (C6, C7)

Extensor carpi radialis longus (ECRL) action

Extend and abduct hand at the wrist joint; ECRL active during first clenching

Extensor carpi radialis brevis [ERCB] proximal attachment (origin)

Lateral epicondyle of humerus (common extensor origin)

Extensor carpi radialis brevis [ERCB] Distal attachment (insertion)

Dorsal aspect of base of 3rd metacarpal

Extensor carpi radialis brevis [ERCB] nerve

Deep branch of radial nerve (C7, C8)

Extensor carpi radialis brevis [ERCB] action

Extend and abduct hand at the wrist joint; ECRL active during first clenching !

Extensor digitorum proximal attachment (origin)

Lateral epicondyle of humerus (common extensor origin) !

Extensor digitorum distal attachment (insertion)

Extensor expansions of medial four digits

Extensor digitorum nerve

Posterior interosseous nerve (C7, C8) continuation of deep branch of radial nerve

Extensor digitorum Action

Extends medial four digits primarily at metacarpophalangeal joints, secondarily at interphalangeal joints

Extensor digiti minimi (EDM) proximal attachment (origin)

Lateral epicondyle of humerus (common extensor origin) *

Extensor digiti minimi (EDM) Distal attachment (insertion)

Extensor expansion of 5th digit

Extensor digiti minimi (EDM) nerve

Posterior interosseous nerve (C7, C8) continuation of deep branch of radial nerve !

Extensor digiti minimi (EDM) Action

Extends 5th digit primarily at metacarpophalangeal joint, secondarily at interphalangeal joint

Extensor carpi ulnaris [ECU] proximal attachment (origin)

Lateral epicondyle of humerus; posterior border of ulna via a shared aponeurosis

Extensor carpi ulnaris [ECU] distal attachment

Dorsal aspect of base of 5th metacarpal

Extensor carpi ulnaris [ECU] nerve

Posterior interosseous nerve (C7,C8) continuation of deep branch of radial nerve *Extensor carpi ulnaris [ECU]

Extensor carpi ulnaris [ECU] action

Extends and adducts hand at wrist joint (also active during first clenching)

Supinator proximal attachment (origin)

Lateral epicondyle of humerus; radial collateral and anular ligaments; supinator fossa; crest of ulna

Supinator distal attachment

Lateral, posterior, and anterior surfaces of proximal third of radius

Supinator nerve

Deep branch of radial nerve (C7,C8)

Supinator action

Supinates forearm; rotates radius to turn palm anteriorly or superiorly (if elbow is flexed)

Extensor indicis proximal attachment (origin)

posterior surface of distal third of ulna and interosseous membraneE

Extensor indicis distal attachment (insertion)

Extensor expansion of 2nd digit

Extensor indicis nerve

Posterior interosseous nerve (C7, C8) continuation of deep branch of radial nerve

Extensor indicis Action

Extends 2nd digit (allowing independent extension); helps extend hand at wrist

Abductor pollicis longus [APL] proximal attachment (origin)

Posterior surface of proximal halves of ulna, radius, and interosseous membrane

Abductor pollicis longus [APL] distal attachment (insertion)

Base of 1st metacarpal

Abductor pollicis longus [APL] nerve

Posterior interosseous (C7 & C8) continuation of deep branch of radial nerve

Abductor pollicis longus [APL] action

Abducts thumb and extends it at carpometacarpal joint

Extensor pollicis longus [EPL] proximal attachment (origin)

Posterior surface of middle third of ulna and interosseous membrane

Extensor pollicis longus [EPL] distal attachment (Insertion)

Dorsal aspect of base of distal phalanx of thumb

Extensor pollicis longus [EPL] nerve

Posterior interosseous (C7 & C8) continuing of deep branch of radial nerve !

Extensor pollicis longus [EPL] Action

Extends distal phalanx of thumb at interphalangeal joint; extends metacarpophalangeal and carpometacarpal joints

Extensor pollicis brevis (EPB) proximal attachment (origin)

Posterior surface of distal 3rd of radius and interosseous membrane

Extensor pollicis brevis (EPB) Distal attachment (insertion)

Dorsal aspect of base of proximal phalanx of thumb

Extensor pollicis brevis (EPB) nerve

Posterior interosseous nerve (C7 & C8) continued of deep branch of radial nerve *

Extensor pollicis brevis (EPB) action

Extends proximal phalanx of thumb at metacarpophalangeal joint; extends carpometacarpal joint