extensor forearm

O -Superficial part-lateral epicondyle of humerus, radial collateral & anular ligaments; deep part-supinator crest of ulna

I -Lateral surface of radius superior to the anterior oblique line

In -Posterior interosseous nerve [C6,C7]

F -Supination

O -Lateral epicondyle of humerus

I -Olecranon & proximal posterior surface of ulna

In -Radial nerve [C6,C7,C8] (via branch to medial head of triceps brachii)

F -Abduction of the ulna in pronation; accessory extensor of elbow joint

O -Lateral epicondyle of humerus & posterior border of ulna

I -Tubercle on base of the medial side of metacarpal V

In -Posterior interosseous nerve [C7,C8]

F -Extends & adducts the wrist

O -Distal part of lateral supraepicondylar ridge of humerus & adjacent intermuscular septum

I -Dorsal surface of base of metacarpal II

In -Radial nerve [C6,C7] before division into superficial & deep branches

F -Extends and abducts the wrist

O -Lateral epincondyle of humerus & adjacent intermuscular septum

I -Dorsal surface of base of metacarpals II & III

In -Deep branch of radial nerve [C7,C8] before penetrating supinator muscle

F -Extends & abducts the wrist

O -Lateral epicondyle of humerus & adjacent intermuscular septum & deep fascia

I -Four tendons, which insert via extensor hoods into the dorsal aspects of the bases of the middle & distal phalanges of the index, middle, ring, & little fingers

In -Posterior interosseous nerve [C7,C8]

F -Extends the index, middle, ring, & little fingers; can also extend the wrist

O -Posterior surface of ulna (distal to extensor pollicis longus) & adjacent interosseous membrane

I -Extensor hood of index finger

In -Posterior interosseus nerve [C7,C8]

F -Extends index finger

O -Lateral epicondyle of humerus & adjacent intermuscular septum together with extensor digitorum

I -Extensor hood of the little finger

In -Posterior interosseous nerve [C7,C8]

F -Extends the little finger

O -Posterior surface of ulna & radius (distal to the attachments of supinator & anconeus), & intervening interosseous membrane

I -Lateral side of base of metacarpal I

In -Posterior interosseous nerve [C7,C8]

F -Abducts carpometacarpal joint of thumb; accessory extensor of the thumb

O -Posterior surface of ulna (distal to the abductor pollicis longus) & adjacent interosseous membrane

I -Dorsal surface of base of distal phalanx of thumb

In -Posterior interosseous nerve [C7,C8]

F -Extends interphalangeal joint of the thumb; can also extend carpometacarpal & metacarpophalangeal joints of the thumb

O -Posterior surface of radius (distal to the abductor pollicis longus) & adjacent interosseous membrane

I -Dorsal surface of base of proximal phalanx of thumb

In -Posterior interosseous nerve [C7,C8]

F -Extends interphalangeal joint of the thumb; can also extend carpometacarpal joint of the thumb

• lateral boundary:
• 1. Tendon of Abductor pollicis longus
• 2. Tendon of Extensor pollicis brevis

• medial boundary:
• 1. Tendon of Extensor pollicis longus

• floor:
• 1. Scaphoid
• 2. Trapezium

• contents:
• - Radial artery

• Compartment 1: Tendons of
• 1. Abductor pollicis longus
• 2. Extensor pollicis brevis

• Compartment 2: Tendons of
• 1. Extensor carpi radialis longus
• 2. Extensor carpi radialis brevis

• Compartment 3: Tendons of
• 1. Abductor pollicis brevis

• Compartment 4: Tendons of
• 1. Extensor digitorum
• 2. Extensor indicis

• Compartment 5: Tendons of
• 1. Extensor digiti minimi

• Compartment 6: Tendons of
• 1. Extensor carpi ulnaris