Forearm Anatomy

Muscles of the Forearm

Muscle	Innervation	Origin	Insertion	Action	Nerve Root
Superficial Flexors
Pronator teres(PT)	median	Med. Epicondyle and coronoid	Mid. Lat. Radius	Pronate, flex, forearm	C6,7 med/lat cords
Flexor carpi radialis(FCR)	median	Med. Epicondyle and coronoid	2nd and 3rd Metacarpal bases	Flex wrist	C6,7,8 med/lat cords
Palmaris Longus(PL)	median	Med. Epicondyle	Palmar aponeurosis	Flex wrist	C7,8,T1 med/lat cords
Flexor carpi ulnaris(FCU)	Ulnar	Med. Epicondlye and post. Ulna	Pisiform	Flex wrist
Flexor digitorum superficialis(FDS)	Median	Med. Epicondyle and ant. Radius	base of middle phalanges	Flex PIP	C7,8,T1 med/lat cords
Deep flexors
Flexor digitorum profundus(FDP)	medain-ant. interoseous and ulnar	Ant. and Med. ulna	Base of distal phalanges	Flex DIP
Flexor pollicis longus	Median-ant. interosseous	Ant. and lat. radius	base of distal phalanxy	Flex IP, thumb
Pronator quadratus	Medain-ant. interosseous	Distal ulna	volar radius	Pronate, hand
Superficial Extensors
Brachioradialis	Radial	Lat.supracondylar humerus	Lat. distal radius	Flex forearm
Ext. carpi radialis longus (ECRL)	Radial	Lat. supracondylar humerus	2nd Metacarpal base	Extend wrist
Ext. carpi radialis brevis (ECRB)	Radial	Lat. epicondyle of humerus	3rd Metacarpal Base	Extend wrist
Anconeus	Radial	Lat. epicondyle of humerus	Prox. dorsal ulna	Extend forearm
Extensor digitorum	Radial-post. interosseous	Lat.epicondyle of humerus	Extensor aponeurosis	Extends digits
Extensor digiti minimi	Radial-post. interosseous	Common extensor tendon	Small finger extensor carpi ulnaris	Extend small finger
Ext. Carpi ulnaris (ECU)	Radial-post. interosseous	Lat. epicondyle of humerus	5th metacapal base	Extend/adduct hand
Deep Extensors
Supinator	Radial-post. interosseous	Lat. epicondyle of humerus, ulna	Dorsoloateral radius	Supinate forearm
Abductor pollicis longus(APL)	Radial-post. interosseous	Dorsal ulna/radius	1st Metacarpal base	abduct thumb,extend
Extensor Pollicis Brevis (EPB)	Radial-post. interosseous	dorsal radius	thumb prox phalangeal base	extend thumb MCP	C6,7,8 post cord
Extensor Pollicis Longus (EPL)	Radial-post. interosseous	dorsolateral ulna	thumb dorsal phalanx base	extend thumb IP	C6,7,8 post cord
Extensor Indicis Proprius (EIP)	Radial-post. interosseous	dorsolateral ulna	index finger extensor apparatus	extend index finger	C6,7,8 post cord

Interosseous Membrane

• function=force transfer from the radius to ulna, muscular origin for several flexor and extensor muscles, maintance of longitudinal forearm stability and support during pronation and suppination 
• McGinley JC, Kozin SH. Interosseous Membrane Anatomy and Functional Mechanics.  CORR 383:108-122

Forearm Cross Sections

Nerves

Anterior Interosseous Nerve (AIN)

• AIN innervated muscles=radial 2 FDP, Flexor pollicis longus, Pronator quadratus. Provides sensation and pain to volar carpus.
• See also AIN syndrome

Lateral Anebrachial Cutaneous

• Beldner S, J Hand Surg Am 2005;30:1226

Martin Gruber