MRI of the forearm

Table 6-1.

Muscles of the Forearm

MUSCLE	ORIGIN	INSERTION	NERVE SUPPLY
Anconeus	Posterior surface of the lateral epicondyle, and adjacent capsular ligament of the elbow	Onto the radial side of the olecranon and adjacent shaft of the ulna	Nerve to anconeus (C7, C8, T1)
Brachioradialis	Upper two thirds of the lateral epicondylar ridge of the humerus and the anterior surface of the lateral intermuscular septum	Lateral side of the base of the styloid process of the radius	Radial (C5, C6, C7)
Extensor carpi radialis longus	Lower third of the lateral epicondylar ridge, lateral intermuscular septum, and extensor tendons from the lateral epicondyle	Lateral aspect of the base of the second metacarpal	Radial (C5, C6, C7)
Extensor carpi radialis brevis	Common extensor tendon from the lateral epicondyle, intermuscular septa, and radial collateral ligament of the elbow joint	Dorsal aspect of the base of the third metacarpal	Radial or deep radial (posterior interosseus) (C7, C8)
Extensor digitorum	Common extensor tendon	Dorsal digital fibrous expansion covering the dorsum of the proximal phalanx and sides of its base, base of the middle, and distal phalanges	Deep radial (posterior interosseus) (C7, C8)
Extensor digiti minimi	Intermuscular septa, overlying fascia, and common extensor tendon	Base of the proximal phalanx of the little finger	Deep radial (posterior interosseus) (C7, C8)
Extensor carpi ulnaris	Two heads: (1) distal dorsal aspect of the lateral epicondyle, and (2) proximal three fourths of the dorsal border of the ulna	Onto a tubercle at the base of the fifth metacarpal	Deep radial (posterior interosseus) (C7, C8)
Supinator	Dorsal aspect of the lateral epicondyle, ulnar depression distal to the radial notch, and supinator crest	Lateral surface of the radius between the anterior and posterior oblique lines	Deep radial (posterior interosseous) (C5, C6)
Abductor pollicis longus	Lateral edge of the proximal part of the middle third of the ulna, adjacent interosseous membrane, dorsal surface of the radius, and, occasionally, the intermuscular septa	Radial side of the ventral aspect of the base of the first metacarpal	Deep radial (posterior interosseus) (C7, C8)
Extensor pollicis brevis	Distal end of the middle third of the radius in its dorsal surface, interosseous membrane, and, occasionally, the ulna	Base of the proximal phalanx of the thumb or into the capsule the metacarpophalangeal joint	Deep radial (posterior of interosseus) (C7, C8)
Extensor pollicis longus	Middle third of the dorsal surface of the ulna adjacent to the interosseous membrane	Base of the distal phalanx of the thumb	Deep radial (posterior interosseus) (C7, C8)
Extensor indicis	Proximal part of the distal third of the posterior surface of the ulna interosseous membrane	Dorsal aponeurosis on the ulnar side of the index finger, adjacent to the base of the proximal phalanx	Deep radial (posterior interosseus) (C7, C8)
Pronator teres	Two heads: (1) humeral head (superior half of the ventral surface of the medial epicondyle), and (2) ulnar head (medial border of the coronoid process)	Onto the middle third of lateral surface of the radius	Median (C6, C7)
Flexor carpi radialis	Medial epicondyle of the humerus	Base of the second metacarpal and usually, base of the third metacarpal	Median (C6, C7)
Palmaris longus	Medial epicondyle	Flexor retinaculum and palmar aponeurosis	Median (C7, C8)
Flexor carpi ulnaris	Two heads: (1) medial epicondyle, and (2) medial side of the olecranon, upper two thirds of the dorsal border of the ulna	Primarily onto the pisiform	Ulnar (C7, C8)
Flexor digitorum superficialis	Two heads: (1) ulnar (ventral surface of the medial epicondyle, ulnar collateral ligament, ulnar tuberosity, medial border of coronoid process), and (2) radial (anterior oblique line and ventral border below the radial oblique line)	Ventral surface of the shaft of the middle phalanx of each finger	Median (C7, C8, T1)
Flexor digitorum profundus	Proximal three fourths of the medial and anterior surface of the ulna and interosseous membrane	Bases of the distal phalanges of the second to fifth digits	Median, anterior interosseous branch (C8, T1)
Flexor pollicis longus	Ventral surface of the radius, oblique line, and adjacent interosseus membrane	Base of the distal phalanx of the thumb	Median, anterior interosseous branch (C8, T1)
Pronator quadratus	Medial side, ventral surface of the distal fourth of the ulna	Distal quarter of the ventral surface of the radius	Median, anterior interosseous branch (C8, T1)