Anatomy Tables - Forearm & Wrist

Osteology
Bone Structure Description Notes
humerus   the bone of the arm (brachium) the humerus articulates proximally with the scapula at the glenoid fossa; it articulates distally with the radius and ulna at the elbow joint
medial supracondylar ridge a narrow ridge running proximally from the medial epicondyle of the humerus the pronator teres m. takes origin from the common flexor tendon near the most inferior part of the medial supracondylar ridge
lateral supracondylar ridge a narrow ridge running proximally from the lateral epicondyle of the humerus it is the site of origin of the brachioradialis m. and the extensor carpi radialis longus m.
lateral epicondyle a knob-like projection on the lateral side of the humerus proximal to the capitulum it is the site of attachment of the common extensor tendon which is the origin of several forearm extensor muscles (extensor carpi radialis brevis m., extensor digitorum m., extensor digiti minimi m., extensor carpi ulnaris m. and supinator m.); inflammation of the attachment of the common extensor tendon is called lateral epicondylitis which is also known as "tennis elbow" (Greek, kondylos = the knob formed by the knuckle of any joint)
medial epicondyle a knob-like projection on the medial side of the humerus proximal to the trochlea it is the attachment site of the common flexor tendon which is the origin for the superficial group of forearm flexor muscles (pronator teres m., flexor carpi radialis m., palmaris longus m., flexor carpi ulnaris m. and flexor digitorum superficialis m.); inflammation of the attachment of the common flexor tendon is called medial epicondylitis which is also known as "golfer's elbow"; the ulnar nerve is in contact with bone as it courses posterior to the medial epicondyle where it is susceptible to injury from blunt trauma or fracture (Greek, kondylos = the knob formed by the knuckle of any joint)
ulna   the bone on the medial side of the forearm (antebrachium) the ulna articulates proximally with the trochlea of the humerus and the head of the radius; it articulates distally with the ulnar notch of the radius (Latin, ulna = elbow or arm)
body the long slender midportion of the ulna it is also called the shaft or diaphysis; the interosseous membrane attaches to the entire length of the interosseous crest of the body of the ulna
radius   the bone on the lateral side of the forearm (antebrachium) the radius pivots on its long axis and crosses the ulna during pronation
body the long, slender midportion of the radius it is also known as the shaft or diaphysis; the interosseous membrane attaches to the entire length of the body of the radius along its interosseous crest; a fracture of the distal end of the body of the radius with a dorsal displacement of the distal fragment is quite common and is called a Colles' fracture
dorsal tubercle lies dorsally between grooves for the passage of the forearm tendons
carpal bones   the bones of the wrist eight bones arranged in two rows; a mnemonic for memorizing the carpal bones is " some lovers try positions that they can't handle" - the first letters of these eight words are the first letters of the names of the eight carpal bones arranged from lateral to medial, proximal row first: scaphoid, lunate, triquetrum, pisiform/trapezium, trapezoid, capitate, hamate
proximal row lateral to medial: scaphoid, lunate, triquetrum, pisiform the scaphoid and lunate bones of the proximal row articulate with the distal end of the radius
distal row lateral to medial: trapezium, trapezoid, capitate, hamate the distal row of carpal bones articulates with the metacarpal bones of the hand
scaphoid   the most lateral carpal bone of the proximal row the scaphoid bone is located in the floor of the anatomical snuff box; it is frequently fractured by hyperextension and abduction of the wrist; (Greek, scaphoid = boat-shaped)
lunate   the carpal bone located between the scaphoid and triquetrum in the proximal row the lunate is so named because it is "moon-shaped" (crescent shaped) in longitudinal section; the head of the capitate sits within the crescent of the lunate (Latin, lunate = lunatus, crescent-shaped, from luna, the moon)
triquetrum   the most medial bone in the proximal row of carpal bones it articulates with the pisiform which sits anterior to it (Latin, triquetrum = having three corners)
pisiform   a sesamoid bone in the tendon of the flexor carpi ulnaris m. it articulates with the triquetrum; the pisiform bone provides a protective function for the flexor carpi ulnaris tendon by bearing the forces generated by the tendon riding across the triquetrum, especially during wrist extension; (Latin, pisiform = pea-shaped)
trapezium   the most lateral carpal bone of the distal row it forms a saddle joint with the metacarpal bone of the thumb; "the thumb swings on the trapezium"
trapezoid   the carpal bone located between the trapezium and the capitate in the distal row the trapezoid is named for its trapezoid shape
capitate   the carpal bone located between the trapezoid and the hamate in the distal carpal row the capitate is the largest carpal bone; it is named for its rounded head; forces generated in the hand (as during a punching blow with the fist) are transmitted through the third metacarpal bone to the capitate and proximally through the lunate to the radius (Latin, capit- = head)
hamate   the most medial carpal bone in the distal row the hamulus (hook) of the hamate is its distinguishing characteristic; it is an attachment point of the flexor retinaculum (Latin, hamus = a hook)
metacarpal bones   the bones located between the carpal bones and the phalanges of the hand there are a total of five metacarpal bones in the hand; the metacarpals of the four fingers are bound together by ligaments to form a firm foundation for finger movements; the metacarpal of the thumb is more independent in its range of motion
base the proximal end of the metacarpal it articulates with the distal row of carpal bones
body the slender shaft of the metacarpal it is also known as the diaphysis
head the rounded distal end of the metacarpal it articulates with the proximal phalanx of the corresponding digit
phalanx (phalanges)   the distal two or three bones in the digits of the hand there are a total of 14 phalanges in the hand; the thumb has two phalanges (proximal and distal) and each finger has three phalanges (proximal, middle and distal); (Latin, phalanx = line of soldiers)
base the proximal end of the phalanx the base of the proximal phalanx articulates with the head of the corresponding metacarpal bone; the base of the middle or distal phalanx articulates with the head of the next most proximal phalanx
body the slender shaft of the phalanx also known as the diaphysis; the body of the distal phalanx is very short
head the distal end of the phalanx the proximal, middle and distal phalanges each have a head; the head of a proximal or middle phalanx articulates with the base of the next most distal phalanx

Topographic Anatomy
Structure/Space Boundaries Significance
antebrachial fascia anterior and posterior thickening forming the extensor retinaculum; immediatel distal but deeper to the palmar carpal ligament it forms the flexor retinaculum formation of the carpal tunnel through which the median n. and flexor tendons pass
anterior compartment separated from the posteror compartment by the interosseous membrane also called the flexor compartment
posteror compartment separated from the anterior compartment by the interosseous membrane also called the extensor compartment
anatomical snuffbox at the base of the thumb; bordered laterally by the tendons of abductor pollicis longus and extensor pollicis brevis, medially by tendon of extensor pollicis longus branches of superficial radial n. cross the snuffbox; radial artery lies deeply in snuffbox; scaphoid can be palpated there in cases of suspected fracture

Joints and Associated Structures of the Forearm

Joint or structure Description Notes
antebrachial fascia the deep fascia of the forearm, or antebrachium, forming a tubular investment around the forearm muscles
extensor retinaculum a thickening of the antebrachial fascia at the wrist it holds the extensor tendons against the distal radius and ulna to prevent their bow-stringing (Latin, retinaculum = a band or halter)
interosseous membrane, forearm a fibrous membrane that connects the interosseous borders located on the shafts of the radius and the ulna a syndesmosis; its fibers are oriented obliquely downward from the radius toward the ulna; the interosseous membrane is the classic example of a syndesmosis; proximally directed forces from the hand pass through the radius and are transferred to the ulna through the interosseous membrane; marked proximally by the oblique cord (Latin, inter = between + os = bone)
palmar carpal ligament a thickening of the antebrachial fascia over the palmar surface of the wrist the palmaris longus and ulnar neurovascular bundle pass deep to it, and the flexor retinaculum lies deeper and more distal
synovial bursa (sheath) synovial sheaths are bursae that stretch along tendons and reduce the friction produced by their movements

Muscles
Muscle Origin Insertion Action Innervation Blood Supply Notes Image
abductor pollicis longus middle one-third of the posterior surface of the radius, interosseous membrane, mid-portion of posterolateral ulna radial side of the base of the first metacarpal abducts the thumb at carpometacarpal joint radial nerve, deep branch posterior interosseous a. the tendons of abductor pollicis longus and extensor pollicis brevis make the lateral border of the anatomical snuffbox (Latin, pollicis = the thumb, from pollere, to be strong, because the thumb is stronger than the other fingers) Image Not Available
brachioradialis upper two-thirds of the lateral supracondylar ridge of the humerus lateral side of the base of the styloid process of the radius flexes the elbow, assists in pronation & supination radial nerve radial recurrent a. although brachioradialis is innervated by the nerve for extensors (radial), its primary action is elbow flexion; the neutral position of this muscle is half way between supination and pronation (elbow flexed, thumb up) Image Not Available
extensor carpi radialis longus lower one-third of the lateral supracondylar ridge of the humerus dorsum of the second metacarpal bone (base) extends the wrist; abducts the hand radial nerve radial a. works with the extensor carpi radialis brevis and flexor carpi radialis in abduction of the hand (Latin, carpus = the wrist)
extensor carpi radialis brevis common extensor tendon (lateral epicondyle of humerus) dorsum of the third metacarpal bone (base) extends the wrist; abducts the hand deep radial nerve radial a. works with the extensor carpi radialis longus and flexor carpi radialis in abduction of the hand (Latin, carpus = the wrist)
extensor carpi ulnaris common extensor tendon & the middle one-half of the posterior border of the ulna medial side of the base of the 5th metacarpal extends the wrist; adducts the hand deep radial nerve ulnar a. works with the flexor carpi ulnaris in adduction of the hand
extensor digiti minimi common extensor tendon (lateral epicondyle of the humerus) joins the extensor digitorum tendon to the 5th digit and inserts into the extensor expansion extends the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints of the 5th digit deep radial nerve interosseous recurrent a. extensor digiti minimi appears to be the ulnar-most portion of extensor digitorum
extensor digitorum common extensor tendon (lateral epicondyle of the humerus) extensor expansion of digits 2-5 extends the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints of the 2nd-5th digits; extends wrist deep radial nerve interosseous recurrent a. and posterior interosseous a. the extensor expansion inserts via a central band on the base of the middle phalanx, while lateral & medial slips insert on the distal phalanx Image Not Available
extensor indicis interosseous membrane and the posterolateral surface of the distal ulna its tendon joins the tendon of the extensor digitorum to the second digit; both tendons insert into the extensor expansion extends the index finger at the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints deep radial nerve posterior interosseous a extensor indicis is a deep forearm extensor, whereas extensor digiti minimi is in the superficial layer of extensors
extensor pollicis brevis interosseous membrane and the posterior surface of the distal radius base of the proximal phalanx of the thumb extends the thumb at the metacarpophalangeal joint deep radial nerve posterior interosseous a the tendons of extensor pollicis brevis and abductor pollicis longus make the lateral border of the anatomical snuffbox, in which the radial arterial pulse can be felt (Latin, pollicis = the thumb, from pollere, to be strong, because the thumb is stronger than the other fingers) Image Not Available
extensor pollicis longus interosseous membrane and middle part of the posterolateral surface of the ulna base of the distal phalanx of the thumb extends the thumb at the interphalangeal joint deep radial nerve posterior interosseous a the tendon of extensor pollicis longus hooks around the dorsal radial tubercle; it forms the medial border of the anatomical snuffbox, in which the radial arterial pulse can be felt (Latin, pollicis = the thumb, from pollere, to be strong, because the thumb is stronger than the other fingers)
flexor carpi radialis common flexor tendon from the medial epicondyle of the humerus base of the second and third metacarpals flexes the wrist, abducts the hand median nerve ulnar a. works with the extensor carpi radialis longus and brevis mm. to abduct hand (Latin, carpus = the wrist)
flexor carpi ulnaris common flexor tendon & (ulnar head) from medial border of olecranon & upper 2/3 of the posterior border of the ulna pisiform, hook of hamate, and base of 5th metacarpal flexes wrist, adducts hand ulnar nerve ulnar a. the ulnar nerve passes between the two heads of origin of the flexor carpi ulnaris m. (Latin, carpus = the wrist)
flexor digitorum profundus posterior border of the ulna, proximal two-thirds of medial border of ulna, interosseous membrane base of the distal phalanx of digits 2-5 flexes the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints median nerve via anterior interosseous branch (radial one-half); ulnar nerve (ulnar one-half) ulnar a., anterior interosseous a. ulnar nerve innervates the portion of profundus that acts on digits 4 & 5 (the ulnar 2 digits)
flexor digitorum superficialis humeroulnar head: common flexor tendon; radial head: middle 1/3 of radius shafts of the middle phalanges of digits 2-5 flexes the metacarpophalangeal and proximal interphalangeal joints median nerve ulnar a. median nerve travels distally in the forearm on the deep surface of the flexor digitorum superficialis m.
flexor pollicis longus anterior surface of radius and interosseous membrane base of the distal phalanx of the thumb flexes the metacarpophalangeal and interphalangeal joints of the thumb median nerve via anterior interosseous branch anterior interosseous a. the tendon of flexor pollicis longus passes through the carpal tunnel with the other long digital flexor tendons and the median nerve (Latin, pollicis = the thumb, from pollere, to be strong, because the thumb is stronger than the other fingers)
pronator quadratus medial side of the anterior surface of the distal one-fourth of the ulna anterior surface of the distal one-fourth of the radius pronates the forearm median nerve via anterior interosseous branch anterior interosseous a. pronator quadratus is the deepest muscle in the distal forearm; it works with pronator teres and has the same nerve supply
palmaris longus medial epicondyle of humerus distal half of flexor retinaculum and palmaris aponeurosis flexes hand (at wrist) and tightens palmar aponeurosis median n. (C7 and C8) ulnar a. palmaris longus is a useful guide to the median nerve at the wrist
pronator teres common flexor tendon and (deep or ulnar head) from medial side of coronoid process of the ulna midpoint of the lateral side of the shaft of the radius pronates the forearm median nerve ulnar a., anterior ulnar recurrent a. median nerve passes between the two heads of origin of pronator teres
supinator lateral epicondyle of the humerus, supinator crest & fossa of the ulna, radial collateral ligament, annular ligament lateral side of proximal one-third of the radius supinates the forearm deep radial nerve recurrent interosseous a. deep radial nerve passes through the supinator to reach the posterior compartment of the forearm (Latin, supinare = to bend backward) Image Not Available
interosseous, dorsal (hand) four muscles, each arising from two adjacent metacarpal shafts base of the proximal phalanx and the extensor expansion on lateral side of the 2nd digit, lateral & medial sides of the 3rd digit, and medial side of the 4th digit flex the metacarpophalangeal joint, extend the proximal and distal interphalangeal joints of digits 2-4, abduct digits 2-4 (abduction of digits in the hand is defined as movement away from the midline of the 3rd digit) ulnar nerve, deep branch dorsal and palmar metacarpal aa. bipennate muscles; remember DAB & PAD - Dorsal interosseous mm. ABduct and Palmar interosseous mm. ADduct - then you can figure out where they must insert to cause these actions (Latin, inter = between + os = bone) Image Not Available
interosseous, palmar four muscles, arising from the palmar surface of the shafts of metacarpals 1, 2, 4, & 5 (the 1st palmar interosseous is often fused with the adductor pollicis m.) base of the proximal phalanx and extensor expansion of the medial side of digits 1 & 2, and lateral side of digits 4 & 5 flexes the metacarpophalangeal, extends proximal and distal interphalangeal joints and adducts digits 1, 2, 4, & 5 (adduction of the digits of the hand is in reference to the midline of the 3rd digit) ulnar nerve, deep branch palmar metacarpal aa. unipennate muscles; remember PAD & DAB: Palmar interossei ADduct and Dorsal interossei ABduct, and you will be able to figure out where they must insert (Latin, inter = between + os = bone)
lumbrical (hand) flexor digitorum profundus tendons of digits 2-5 extensor expansion on the radial side of the proximal phalanx of digits 2-5 flex the metacarpophalangeal joints, extend the proximal and distal interphalangeal joints of digits 2-5 median nerve (radial 2) via palmar digital nerves & ulnar nerve (ulnar 2) via deep branch superficial palmar arterial arch lumbricals, (lumbricus is latin for "worm") arise from the profundus tendons and have the same pattern of innervation as does the profundus muscle (ulnar and median nn. split the task equally) (Latin, lumbricus = earthworm)

Arteries
Artery Source Branches Supply Notes
arch, superficial palmar ulnar a., superficial palmar br. of the radial a. common palmar digital aa. (3) superficial palm, palmar surface of the digits excluding thumb, dorsum of the distal phalangeal segments of digits 2-5 superficial palmar arterial arch receives the majority of its blood supply from the ulnar a.
brachial axillary a. (brachial a. is the continuation of the axillary a. distal to the teres major m.) deep brachial a., superior ulnar collateral a., nutrient a., inferior ulnar collateral a.; terminal branches are the radial a. and the ulnar a. arm, forearm and hand brachial a. normally terminates at the level of the elbow, but high branching may occur
interosseous, anterior common interosseous a. muscular brs.; a. of the median nerve flexor pollicis longus m., flexor digitorum profundus m., pronator quadratus m., radius, ulna, carpal bones anterior interosseous a. pierces the interosseous membrane at its distal end to reach the dorsal carpal anastomosis (Latin, inter = between + os = bone)
interosseous, common ulnar a. anterior interosseous a., posterior interosseous a. deep structures of the forearm common interosseous a. supplies the deep forearm flexor and deep forearm extensor muscles (Latin, inter = between + os = bone)
interosseous, posterior common interosseous a. interosseous recurrent muscles of the posterior (extensor) forearm compartment: supinator m., abductor pollicis longus m., extensor pollicis longus m., extensor pollicis brevis m., extensor indicis m. posterior interosseous a. passes proximal to the interosseous membrane to reach the extensor compartment of the forearm (Latin, inter = between + os = bone)
radial brachial a. radial recurrent a., palmar carpal br., superficial palmar br., dorsal carpal br., 1st dorsal metacarpal a., princeps pollicis a., radialis indicis a., deep palmar arterial arch posterior elbow, posterior forearm, posterior hand, deep portion of palmar side of the hand, thumb radial a. provides the majority of blood supply to the deep palmar arterial arch; normally it arises at the level of the elbow but high branching of the brachial a. may result in the radial a. arising as proximal as the axilla
ulnar brachial a. anterior ulnar recurrent a., posterior ulnar recurrent a., common interosseous a., palmar carpal br., dorsal carpal br., deep palmar br., superficial palmar arterial arch medial side of the anterior forearm, posterior forearm, superficial palm, fingers ulnar a. supplies the majority of blood to the superficial palmar arterial arch; it normally arises at the level of the elbow, but high branching of the brachial a. may cause the ulnar a. to arise as far proximally as the axilla (Latin, ulna = elbow or arm)

Nerves
Nerve Source Branches Motor Sensory Notes
interosseous, anterior median n. no named branches flexor pollicis longus m., radial half of flexor digitorum profundus m., pronator quadratus m. none courses along the anterior surface of the interosseous membrane (Latin, inter = between + os = bone)
interosseous, posterior deep radial n. no named branches some authors say none, others say the deep posterior forearm muscles proprioception to the wrist joint there is variability in the definition of this nerve; for some, deep radial and posterior interosseous are synonymous; others define this nerve as the articular br. to the wrist from the deep radial (Latin, inter = between + os = bone)
median n. lateral and medial cords of the brachial plexus anterior interosseous n., palmar br., recurrent (motor) br., common palmar digital nn. (for digits 1-3) pronator teres m., flexor carpi radialis m., palmaris longus m., flexor digitorum superficialis m., flexor digitorum profundus m. (radial half), flexor pollicis longus m., pronator quadratus m., abductor pollicis brevis m., flexor pollicis brevis m., opponens pollicis m., lateral 2 lumbrical mm. skin of the radial half of the palm and palmar side of the lateral 3 1/2 digits (and nail bed for these digits) the median n. is motor to the flexor muscles of the forearm (except flexor carpi ulnaris and the medial 1/2 of the flexor digitorum profundus),the muscles of the thenar compartment and the lateral 2 lumbricals
radial n. posterior cord of the brachial plexus posterior brachial cutaneous n., inferior lateral brachial cutaneous n., posterior antebrachial cutaneous n., superficial and deep brs. muscles of the posterior arm: triceps brachii m., anconeus m.; muscles of the posterior forearm: brachioradialis, extensor carpi ulnaris m., extensor carpi radialis longus m., extensor carpi radialis brevis m., extensor digitorum m., extensor digiti minimi m., supinator m., abductor pollicis longus m., extensor pollicis longus m., extensor pollicis brevis m., extensor indicis m. skin of the posterior arm, forearm and hand all of the muscles on the posterior side of the arm and forearm are innervated by the radial n.
radial, deep radial n. posterior interosseous n. extensor carpi radialis brevis m., supinator m., extensor digitorum m., extensor digiti minimi m., abductor pollicis longus m., extensor pollicis longus m. extensor pollicis brevis m., extensor indicis m. no cutaneous branches deep radial n. passes through the supinator m.; some authors believe that the posterior interosseous n. and the deep radial n. are synonymous, others say that when the deep radial n. emerges from the supinator in the posterior forearm it becomes the posterior interosseous n., and others say that the deep radial n. does not become the posterior interosseous n. until after its last muscular br. has been given off
radial, superficial radial n. dorsal digital brs. sympathetic motor for the skin skin of the posterolateral wrist and hand; dorsum of the lateral 2 1/2 digits (excluding the skin over the distal phalanx/nail bed) superficial radial n. is located deep to the brachioradialis muscle
ulnar n. medial cord of the brachial plexus (C8, T1) palmar cutaneous br., dorsal br., superficial and deep brs. flexor carpi ulnaris m., flexor digitorum profundus m. (ulnar half), abductor digiti minimi m., flexor digiti minimi brevis m., opponens digiti minimi m., ulnar 2 lumbrical mm., palmar and dorsal interosseous mm. skin of the medial side of the wrist and hand; skin of the medial 1 1/2 digits ulnar n. is motor to most of the muscles of the hand (Latin, ulna = elbow or arm)

Clinical Terms
Term Definition
Colles fracture most common fracture of the forearm. The distal end of the radius is broken, and distal fragment is displaced dorsally and is often comminuted (broken into pieces). The fracture results from forced extension of the hand, usually as the result of trying to ease a fall by outstretching the upper limb.
tennis elbow also called elbow tendinitis, it is due to repetitive use of the superficial extensor muscles of the forearm. The pain is felt on the lateral epicondyle and radiates down the posterior surface of the forearm. Patients with this condition will often feel pain when they open a door or lift a glass. The repeated forceful flexion and extension of the wrist strains the attachment of the common tendon, producing inflammation of the periosteum of the lateral epicondyle and the common extensor attachment of the muscles.
epicondylitis inflammation of the epicondyle or of the tissues adjoining the epicondyle of the humerus. Lateral epicondylitis is also referred to as "tennis elbow". (Greek, kondylos = the knob formed by the knuckle of any joint)
scaphoid fracture/avascular necrosis scaphoid is the most frequently fractured carpal bone, and injury to this bone is the most common wrist injury. Pain occurs primarly during extension and abduction of the hand, and is felt on the lateral side of the wrist. Because of poor blood supply to the proximal part of the scaphoid, union of the fractured parts may take several months. Avascular necrosis of the proximal fragment of the scaphoid may occur and produce degenerative joint disease of the wrist. In some cases, it is necessary to fuse the carpals surgically.
wrist drop the radial nerve is usually injured when the humeral shaft fractures. An injury of this kind is going to be proximal to the wrist extensors, thus wrist drop is a common clinical manifestation. The deep branch of the radial nerve can be injured by deep puncture wounds to the forearm. The deep branch of the radial nerve is responsible for extending the thumb and MP joints. Neither deep nor superficial radial nerve injury causes much sensory loss, but cutting the superficial leaves a coin-shaped area distal to the bases of the 1st and 2nd metacarpals without sensation.

The material presented in these tables is contained in the book:
MedCharts Anatomy by Thomas R. Gest & Jaye Schlesinger
Published by ILOC, Inc., New York
Copyright © 1995, unauthorized use prohibited.
 The excellent editorial assistance of
Dr. Pat Tank, UAMS
is gratefully acknowledged.

Copyright© 2000 The University of Michigan. Unauthorized use prohibited.
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