Superficial posterior forearm muscles

Brachioradialis muscle

The brachioradialis is a long, fusiform muscle and the most superficially situated one from the group, extending on the radial side of the forearm. It arises from the lateral supracondylar ridge of humerus and the anterior surface of the lateral intermuscular septum of the arm. From here, the muscle descends distally, extending into a tendon that inserts proximally to the styloid process of radius.

The brachioradialis muscle is innervated by the radial nerve (C5-C7). The blood supply for this muscle comes from the radial recurrent branch of the radial artery, and the radial collateral branch of the deep brachial artery.

The prime function of this muscle is to flex the forearm, which is most efficient when the forearm is semi-pronated. The brachioradialis muscle acts in synergy with other flexors of the forearm, which include the biceps brachii and brachialis muscles.

Extensor carpi radialis longus

The extensor carpi radialis longus is a long muscle located on the lateral (radial) aspect of the forearm. It arises from the lateral supracondylar ridge of humerus and the lateral intermuscular septum of the arm. The muscle then descends distally, ending in a narrow tendon that inserts onto the base of metacarpal bone of the 2nd digit.

The extensor carpi radialis longus muscle receives its innervation via the radial nerve (C6, C7). It is vascularized mainly by the radial artery, with some contributions from the deep brachial artery, via the radial collateral artery.

The extensor carpi radialis mainly acts on the wrist joint, producing extension and abduction (radial deviation) of the hand. Thereby, the extensor carpi radialis is one of the key muscles in the anatomy of the grip. Additionally, it contributes to the flexion of the forearm at the elbow joint.

Extensor carpi radialis brevis

The extensor carpi radialis brevis is a fusiform muscle located deep to its long counterpart, the extensor carpi radialis brevis muscle. It arises from the lateral epicondyle of humerus via the common extensor tendon, shared with the extensor digitorum, extensor carpi ulnaris and extensor digiti minimi muscles. The muscle fibers then descend towards the wrist where they converge onto a long tendon that inserts on the posterior aspect of the base of metacarpal bone of the 3rd digit.

The extensor carpi radialis brevis receives its innervation by the deep branch of the radial nerve (C7, C8). The blood supply for this muscle is conveyed mainly by the radial artery, with contributions from the deep brachial artery via its radial collateral branch.

The extensor carpi radialis brevis works in synergy with the extensor carpi radialis longus to extend and abduct the hand at the wrist joint.

Extensor digitorum muscle

The extensor digitorum is a long fusiform muscle originating on the lateral epicondyle of the humerus via the common extensor tendon. From here, the muscle fibers run distally, extending into four separate tendons that insert onto the extensor expansions of digits 2-5, respectively.

The extensor digitorum muscle is innervated by the posterior interosseous nerve (C7, C8). It receives its blood supply mainly via the posterior interosseous artery with contributions from the radial recurrent and anterior interosseous arteries.

The extensor digitorum is the main extensor of the second to fifth digits in the metacarpophalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal joints (DIP). Additionally, this muscle also contributes to the extension of the hand at the wrist joint.

Start with the anatomy of the forearm muscles by exploring our videos, quizzes, labeled diagrams and articles.

Extensor carpi ulnaris muscle

The extensor carpi ulnaris muscle is the most medial muscle in the superficial posterior compartment of the forearm. It originates from the lateral epicondyle of humerus via the common extensor tendon. The muscle fibers then descend towards the wrist area where they converge onto a narrow tendon that passes along the dorsum of the hand to insert onto the base of metacarpal bone of the 5th digit.

Similarly to previous muscles, extensor carpi ulnaris is innervated by the posterior interosseous nerve (C7, C8) and vascularized by the radial recurrent and posterior interosseous arteries.

Its prime function is adduction (ulnar deviation) of the hand at the wrist joint. It also contributes to the balanced extension of the hand when working in synergy with the radial extensors (extensor carpi radialis brevis and extensor carpi radialis longus).

Feeling a bit overwhelmed? Learn the attachments, innervation and functions of the superficial posterior forearm muscles faster and easier with our muscle charts!

Extensor digiti minimi muscle

The extensor digiti minimi is a thin muscle situated just medial to the extensor digitorum muscle. This muscle also originates from the lateral epicondyle of humerus via the common extensor tendon. The muscle then runs distally, extending into a tendon that inserts onto the extensor expansion of digit 5.

The extensor digiti minimi muscle is innervated by the posterior interosseous nerve (C7, C8). It receives its blood supply via the radial recurrent, and the anterior and posterior interosseous arteries.

Like the name of the muscle indicates, the main function of extensor digiti minimi is to extend the fifth digit at its metacarpophalangeal (MCP) joint, but it may also act on other joints of the fifth digit. In addition, it contributes to the extension of the hand at the wrist joint.

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