Origin: Proximal 2/3 of supracondylar ridge of humerus.

Insertion: Lat. surface of distal end of radius proximal to styloid process.

Action: Weak forearm flexion (maximal in mid-pronated/mid-supinated position)

Inervation: Radial n. (C5, C6, C7)

Extensor Carpi Radialis Longus

(ECRL)

Origin: Lat. supracondylar ridge of humerus.

Insertion: Dorsal aspect, base of 2nd metacarpal.

Action: Extension and radial deviation of wrist; active during fist clenching.

Inervation: Radial n. (C6, C7)

Extensor Carpi Radialis Brevis

(ECRB)

Origin: Lateral epicondyl of humerus via common extensor tendon.

Insertion: Dorsal aspect, base of 3rd metacarpal.

Action: Extension and radial deviation of wrist.

Inervation:  Deep branch of radial n. (C7, C8).

Blood Supply: Radial a.

Extensor Digitorum

(ED)

Origin: Lateral epicondyle via common extensor tendon.

Insertion: Dorsal digital expansion (DDE) of med. four digits; AKA extensor expansion.

Action: Extension of med. 4 digits primarily at MCPs, secondarily at IPs.

Inervation: Deep branch of radial n. (C7, C8)

Extensor Digiti Minimi

(EDM)

Origin: Lateral epicondyle via common extensor tendon.

Insertion: DDE of 5th metacarpal.

Action: Extension of 5th digit primarily at MCP, secondarily at IP.

Inervation: Deep branch of radial n.

Extensor Carpi Ulnaris

(ECU)

Origin: Lat. epicondyle of humerus; post. border of ulna via shared aponeurosis.

Insertion: Dorsal aspect, base of 5th metacarpal.

Action: Extension and ulnar deviation of wrist; also active during fist clenching.

Inervation: Deep branch of radial n.

Origin: Lat. epicondyle of humerus.

Insertion: Lat. surface of olecranon and sup. part of post. surface of ulna.

Action: Assists w/ forearm extension; stabilizes elbow joint; may ABD ulna during pronation.

Inervation: Radial n. (C7, C8, T1)