Muscles of the anterior compartment of the forearm

Muscle	Proximal attachment	Distal attachment	Innervation*	Main action
Superficial (first) layer
Pronator teres		Middle of convexity of lateral surface of radius	Median nerve (C6, C7)	Pronates and flexes forearm (at elbow)
Ulnar head	Coronoid process
Humeral head	Medial epicondyle of humerus (common flexor origin)
Flexor carpi radialis (FCR)		Base of second metacarpal		Flexes and abducts hand (at wrist)
Palmaris longus		Distal half of flexor retinaculum and apex of palmar aponeurosis	Median nerve (C7, C8)	Flexes hand (at wrist) and tenses palmar aponeurosis
Flexor carpi ulnaris (FCU)				Flexes and adducts hand (at wrist)
Humeral head		Pisiform, hook of hamate, fifth metacarpal	Ulnar nerve (C7, C8)
Ulnar head	Olecranon and posterior border (via aponeurosis)
Intermediate (second) layer
Flexor digitorum superficialis (FDS)	Medial epicondyle (common flexor origin and coronoid process)	Shafts (bodies) of middle phalanges of medial four fingers	Median nerve (C7, C8, T1)	Flexes middle phalanges at proximal interphalangeal joints of middle four fingers; acting more strongly, it also flexes proximal phalanges at metacarpophalangeal joints
Humeroulnar head
Radial head	Superior half of anterior border
Deep (third) layer
Flexor digitorum profundus (FDP)	Proximal three quarters of medial and anterior surfaces of ulna and interosseous membrane	Bases of distal phalanges of fourth and fifth fingers	Ulnar nerve (C8, T1)	Flexes distal phalanges four and five at distal interphalangeal joints
Medial part
Lateral part			Anterior interosseous nerve, from median nerve (C8, T1)	Flexes distal phalanges two and three at distal interphalangeal joints
Flexor pollicis longus (FPL)	Anterior surface of radius and adjacent interosseous membrane	Base of distal phalanx of thumb		Flexes phalanges of first digit (thumb)
Pronator quadratus	Distal quarter of anterior surface of ulna	Distal quarter of anterior surface of radius		Pronates forearm; deep fibers bind radius and ulna together

* The spinal cord segmental innervation is indicated (eg, "C6, C7" means that the nerves supplying the pronator teres are derived from the sixth and seventh cervical segments of the spinal cord). Numbers in boldface (C7) indicate the main segmental innervation. Damage to one or more of the listed spinal cord segments or to the motor nerve roots arising from them results in paralysis of the muscles concerned.

Reproduced with permission from: Moore KL, Dalley AR. Clinically Oriented Anatomy, 5th ed, Lippincott Williams & Wilkins, Philadelphia 2006. Copyright © 2006 Lippincott Williams & Wilkins. www.lww.com.

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Muscles of the anterior compartment of the forearm