Posterior Forearm

The posterior compartment of the forearm is between the elbow and wrist joints, contains 12 muscles divided into superficial and deep groups

1. POSTERIOR FOREARM By- Henan Fatemah Pathan Group 92

2. WHAT ARE THE MUSCLES OF POSTERIOR FOREARM? The forearm is divided into compartments; the flexor (anterior) compartment, and the extensor (posterior) compartment. The posterior compartment of the forearm contains 11 muscles which share a common function of extending the hand and digits and are thus called the extensor muscles of the forearm. The extensors of the forearm are further subdivided into a superficial and deep layer. Most of the muscles in the superficial layer have a common origin on the lateral epicondyle of the humerus, while the muscles of the deep layer typically originate from the distal part of the ulna.

3. 11 The posterior compartment of the forearm contains 11 muscles, divided into deep and superficial layers.

4. Muscles of the posterior compartment of the forearm are: Superficial- 6 muscles. Deep- 5 muscles.

5. Superficial layer of the posterior compartment The superficial posterior forearm muscles are a group of six muscles situated in the superficial layer of the posterior compartment of the forearm. These muscles include the brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor carpi ulnaris and extensor digiti minimi.

6. BRACHIORADIALIS The brachioradialis is a long, fusiform muscle and the most superficially situated one from the group, extending on the radial side of the forearm. The prime function of this muscle is to flex the forearm, which is most efficient when the forearm is semi-pronated.

7. 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 extensor carpi radialis mainly acts on the wrist joint, producing extension and abduction of the hand. 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.

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

9. EXTENSOR DIGITORUM The extensor digitorum is a long fusiform muscle originating on the lateral epicondyle of the humerus via the common extensor tendon. This muscle contributes to the extension of the hand at the wrist joint.

10. EXTENSOR CARPI ULNARIS 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. Its prime function is adduction 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).

11. EXTENSOR DIGITI MINIMI 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. It contributes to the extension of the hand at the wrist joint.

12. FUNCTION OF SUPERFICIAL POSTERIOR FOREARM MUSCLES The superficial posterior forearm muscles act together to produce movements of the forearm, hand and fingers. More specifically, these muscles produce: Flexion of the forearm at the elbow joint. Extension, adduction and abduction of the hand at the wrist joint.

13. Deep layer of the posterior compartment The deep posterior forearm muscles are a group of five muscles located in the deep layer of the posterior compartment of the forearm. These muscles include the supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus and extensor indicis.

14. SUPINATOR The supinator muscle lies in the proximal aspect of the forearm surrounding the upper third of the radius. The prime action of the supinator muscle is to rotate the radius at the proximal radioulnar joint, bringing the radius in a parallel position to the ulna. This results in the supination of the forearm, which is essentially an external rotation of the forearm in which the palm of the hand is facing upwards.

15. ABDUCTOR POLLICIS LONGUS The abductor pollicis longus is a long muscle that originates from the posterior aspect of the proximal half of the radius and ulna, and the adjacent interosseous membrane. The name of the muscle points to its prime function of abducting the thumb at the first metacarpophalangeal joint. Additionally, the abductor pollicis longus is an important contributor to the extension of the thumb at the metacarpophalangeal joint, and abduction of the hand at the radiocarpal joint.

16. EXTENSOR POLLICIS BREVIS The extensor pollicis brevis is a short, posterior forearm muscle that originates from the distal third of the radius and the adjacent interosseous membrane, and inserts onto the base of the proximal phalanx of the thumb. This muscle primarily acts as an extensor of the thumb at the carpometacarpal and metacarpophalangeal joints. It contributes to the movements in the wrist joint, primarily to the extension of the hand.

17. EXTENSOR POLLICIS LONGUS The extensor pollicis longus is a slender muscle that extends across the distal half of the forearm. The prime function of extensor pollicis longus is to extend the thumb in the metacarpophalangeal and interphalangeal joints. This action occurs in synergy with the action of extensor pollicis brevis muscle. Additionally, extensor pollicis longus contributes to the extension and abduction of the hand at the wrist joint.

18. EXTENSOR INDICIS The extensor indicis is a narrow fusiform muscle found in the distal aspect of the forearm. The prime action of extensor indicis is the extension of the index finger at the metacarpophalangeal and interphalangeal joints. As it crosses the wrist joint, the extensor indicis also contributes to the extension of the hand.

19. FUNCTION OF DEEP POSTERIOR FOREARM MUSCLES The deep posterior forearm muscles act together to produce movements of the hand and fingers. The prime functions of these muscles are to extend the hand at the wrist joint, extend the first and second digits at the metacarpophalangeal (MCP) and interphalangeal (IP) joints and to abduct the thumb.

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