Functional Anatomy of the Wrist

Original Editor - Ewa Jaraczewska

Top Contributors - Ewa Jaraczewska, Jess Bell and Kim Jackson  

Introduction

The wrist joint has two degrees of freedom: flexion and extension and radial and ulnar deviation. Both flexion and extension occur in the proximal and distal rows of the carpal bones. The radial and ulnar deviation occurs when wrist alignment alters: during the radial deviation, the proximal row flexes, and the distal row extends. In ulnar deviation, the proximal row extends and the distal row flexes. The ligamentous stabilisers and proximal forearm muscles control this two-dimensional wrist motion. In addition, the distal radioulnar joint motion of pronation and supination is essential for the normal function of the upper limb.

The functional range of the wrist required to perform basic activities of daily living is 30 degrees of extension, 5 degrees of flexion, 10 degrees of radial deviation, and 15 degrees of ulnar deviation. However, the actual motion required to complete each individual task is much higher, according to Nelson et al. Optimal wrist function allows for the performance of activities of daily living, which leads to independent living and improves quality of life.

This article discusses the key anatomical structures of the wrist complex, including the bony structures, articulations, ligaments, muscles, nerves and the vascular supply.

Key Terms

Axes: lines around which an object rotates. The rotation axis is a line that passes through the centre of mass. There are three axes of rotation: sagittal passing from posterior to anterior, frontal passing from left to right and  vertical passing from inferior to superior. The rotation axes of the foot joints are perpendicular to the cardinal planes. Therefore, motion at these joints results in rotations within three planes. Example: supination involves inversion, internal rotation, and plantarflexion.

Bursae: reduces friction between the moving parts of the body joints. It is a fluid-filled sac. There are four types of bursae: adventitious, subcutaneous, synovial, and sub-muscular.

Capsule: one of the characteristics of the synovial joints. It is a fibrous connective tissue that forms a band that seals the joint space, provides passive and active stability and may even form articular surfaces for the joint. The capsular pattern is "the proportional motion restriction in range of motion during passive exercises due to tightness of the joint capsule."

Closed pack position: the position with the most congruency of the joint surfaces. In this position, joint stability increases. The closed pack position for interphalangeal joints is a full extension.

Degrees of freedom: the direction of joint movement or rotation; there is a maximum of six degrees of freedom, including three translations and three rotations.

Ligament: fibrous connective tissue that holds the bones together.

Open (loose) pack position: position with the least joint congruency where joint stability is reduced.

Planes of movement: describe how the body moves. Up and down movements (flexion/extension) occur in the sagittal plane. Sideway movements (abduction/adduction) occur in the frontal plane. The transverse plane movements are rotational (internal and external rotation).

Wrist Structure

The wrist structure includes three joints, distal ends of the two forearm bones, seven carpal bones and proximal bases of the metacarpal bones:

• Distal ulna and distal radius make up the distal radioulnar joint
• The scaphoid, the lunate, and the triquetrum, which are proximal carpal bones and the radius are part of the radiocarpal joint
• The trapezium, trapezoid, capitate, and hamate bones are the distal carpal bones. Together with the proximal carpal bones, they make up the midcarpal joint.
• The pisiform is the fourth bone located in the proximal row. It does not, however, articulate as part of the radiocarpal joint, as it sits on top of the triquetrum.

Distal ulna: includes the ulnar head and the styloid process.

• Ulnar head has two articular surfaces: lateral and inferior
  • The lateral surface, which is convex, articulates with the ulnar notch of the distal radius.
  • The inferior surface articulates with an articular disc (the triangular fibrocartilage).
  • Due to its articulation with the disc, the head of the distal ulna is separated from the carpal bones and therefore does not directly contribute to the wrist joint.
• Styloid process: short and rounded. Can be palpated at the dorsomedial aspect of the wrist.

Distal radius: contains four articular surfaces and a dorsal tubercle, known as Lister’s tubercle

• Articular surfaces
  • Concaved anterior surface
  • The medial surface with its concaved ulnar notch for holding the head of the ulna
  • The lateral surface with its radial styloid process
  • The inferior surface with two facets articulating with two carpal bones: the scaphoid and lunate
• Dorsal tubercle located on the posterior surface

Carpal Bones

Proximal raw:

The scaphoid (navicular): belongs to the proximal raw of the carpal bones. Located the most laterally. Its palmar surface contains the tubercle, the attachment point for the muscles and the floor for the anatomical snuffbox.

The lunate: part of the proximal raw of the carpal bones. It articulates with the scaphoid on the lateral and with the triquetrum on the medial side.

The triquetrum: other names include triquetral, triangular, or cuneiform bone. It is a triangular and pyramidal-shaped bone located in the proximal raw, on the medial side of the wrist. It contains multiple articulation surfaces: lateral for the lunate, anterior for the pisiform, and distal for the hamate.

Distal raw:

The trapezium: located in the distal raw of the carpal bones, on its radial side. It has four articulations for the first metacarpal, second metacarpal, scaphoid and trapezoid bones. This bone is part of the mechanism responsible for the wide mobility of the human hand, where the articulation between the first metacarpal and the trapezium allows for the opposable thumbs function.

The trapezoid: The lesser multangular bone is another name for this bone. This is the smallest bone of the distal raw of the carpal bones. It gives structure to the palm of the hand.

The capitate: the largest and most central carpal bone belonging to the distal raw. It articulates with the bases of the 2nd and 3rd metacarpal bones forming part of the common carpometacarpal joint in the hand. In addition, it articulates with the following: scaphoid and lunate on the proximal, trapezoid on the lateral, and the hamate on the medial surfaces.

The hamate: sits on the medial side of the distal row of carpal bones. The hook of the hamate is the bony process extending from the palmar surface. This carpal bone forms the medial border of the carpal tunnel.

Bones, Articulations and Kinematics of the Wrist

Wrist mobility depends on the interaction between the seven carpal bones and the radius. The ulna and the pisiform are excluded from this motion as the pisiform is a sesamoid bone, and the ulna is separated from the carpal bones by the disc. Each carpal bone has a separate motion axis. However, their movement depends on the carpal alignment with the distal radius.

The greatest degree of motion occurs between the radius and the proximal row of the carpal bones, and less motion occurs between the proximal and distal rows. There is no motion between the distal row of the carpal bones and the metacarpals. The wrist's proximal row is responsible for maintaining wrist stability, while the distal row supports the bases of the metacarpals.

The wrist biomechanics can be described by the following theories:

• The row theory when the carpal bones are grouped into proximal and distal raws
• The column theory when the central column includes the lunate, the capitate, and the hamate; the lateral column (described as the mobile column) includes the scaphoid, the trapezium, and the trapezoid; and the medial column ( rotation column), contains the triquetrum and the pisiform.
• The row-column-theory, which is the modified column-theory. The trapezium and trapezoid were added to the central column, and the pisiform was eliminated from the medial column.
• The ring model where the wrist has two mobile links: the mobile trapezioscaphoid articulation and the rotatory triquetrohamate joint.
• The link joint-theory with the radius, the proximal raw and the distal raw comprising the individual links.
• The clamp theory is where bones are "clamped" into masses: the scaphoid bone as one mass, the lunate and triquetrum as the second mass, and the hamate, capitate, and trapezoid as a distal mass.

Bones and Articulations

Bones	Articulations	Characteristics	Key palpation points
Distal ulna Distal radius	Distal radioulnar joint	Essential joint for forearm rotation When forearm supination and pronation are lost, it significantly affects the function of the upper limb
Proximal articulation: Distal radius Articular disc Distal articulation: Scaphoid Lunate Triquetrum	Radiocarpal	A major synovial joint of the wrist. It contains the concaved surface of the distal end of the radius, the articular disc of the distal radioulnar joint, and the convexed surface of the proximal carpal row. The combined motion of midcarpal and radiocarpal joints makes up the total range of wrist motion.	The lunate is located just below the capitate, in the proximal articulation of the wrist joint (see below for the palpation of the capitate). You can verify your palpation by making the lunate "pop-up" when fully flexing the wrist. The scaphoid bone can be palpated on the volar side. First, find the tubercle of the scaphoid in the thenar eminence. The tender spot on the thenar eminence is the tubercle. Turn the hand with the dorsal side up. Locate the snuff box by resisting thumb extension. You will see the snuff box at the base of the thumb. The rest of the scaphoid bone can be palpated inside the snuff box. To palpate the triquetrum, position the patient's hand with the ulnar side up. Place your finger on the ulnar side of the patient's hand, just above the ulnar styloid process. Ask the patient to deviate the wrist towards the radial side. The triquetrum bone will pop up under your finger.
Proximal articulation: Scaphoid Lunate Triquetrum Distal articulation: Trapezium Trapezoid Capitate Hamate	Midcarpal	Articulation of proximal and distal carpal rows. In particular, the midcarpal motion includes the combined motion of three types of joint systems: between the scaphoid and the distal raw, between the lunate and triquetrum and the distal row, and the intercarpal joints of the proximal row.	Place your finger on the thumb and slide it down to the first metacarpal to locate the trapezium. Just below the first metacarpal, you will palpate a light indentation, which is the landmark for the trapezium bone. The trapezoid bone is located between the trapezium and the capitate. To find the capitate, slide your finger down along the middle finger to reach the third metacarpal bone. You have located the capitate bone when your finger drops into a duvet (indentation) To palpate the hamate bone, first locate the hook of the hamate. Turn the patient's hand with the palmar (volar) side up and place your finger on the hypothenar region. You can palpate the hook and the hamate bone in the hypothenar eminence. The hook of the hamate is tender, and gentle compression on the bone may be unpleasant for the patient.

Wrist Kinematics

The wrist kinematics is essential in completing the activities of daily living. The following are the examples of wrist involvement in a specific task:

• Pouring water from a jug into a cup: requires a stable wrist in the sagittal and coronal planes and the ability to complete pronation/supination motion.
• Turning a key in a mortice lock: uses a lateral pinch and requires forearm pronation and supination
• Cutting with a knife: requires a stable wrist with a challenging and stable volar grip
• Zipping and unzipping a jacket: needs stable wrist in flexion, with the rest of the motion coming from the elbow and shoulder
• Lifting a laden plate: requires forearm pronation/supination until contact is made with an extension grip on the plate. The wrist is maintained in a stable position in all three planes until the laden plate is released.

Joint	Type of joint	Plane of movement	Motion	Kinematics	Closed pack position	Open pack position
Distal radioulnar	Synovial joint-uniaxial pivot joint	Transverse	Pronation Supination	Pronation:80 degrees Supination: 85 degrees	5 degrees of supination	10 degrees of supination
Radiocarpal	Synovial joint-multiaxial ellipsoid joint	Saggital Frontal	Flexion (40%) Extension (66%) Ulnar deviation (50%) Radial deviation (10%) Circumduction (circular hand motions about the wrist)	Flexion: 65-80 degrees Extension:55-65 degrees	Extension with a slight degree of abduction and radial deviation	Neutral with a small degree of adduction and ulnar deviation.
Midcarpal	Synovial joint-gliding joint	Saggital Frontal	Flexion (60%) Extension (33%) Radial deviation (90%) Ulnar deviation (50%)	Ulnar deviation:30-35 degrees Radial deviation:15-25 degrees	Extension with ulnar deviation	Neutral or slight flexion with ulnar deviation

Wrist Passive Range of Motion Assessment

Wrist Flexion

• Patient seated with the upper arm supported on the table and the wrist off the table.
• With the elbow straight, the distal arm of the goniometer is placed along the third metacarpal. The proximal arm of the goniometer is held along the dorsal aspect of the distal forearm.
• Perform wrist flexion.
• Assess the end feel.
• The normal flexion angles should measure approximately 80 degrees.

Wrist Extension

• Patient seated with the upper arm supported on the table and the wrist off the table.
• With the elbow straight, the distal arm of the goniometer is placed along the third metacarpal. The proximal arm of the goniometer is held along the dorsal aspect of the distal forearm.
• Perform wrist extension.
• Assess the end feel.
• The normal extension angles should measure approximately 65 degrees.

Wrist Radial Deviation

• Patient seated with the forearm in pronation resting on a table.
• The elbow flexed to 90 degrees, and the arm is slightly abducted.
• One goniometer arm is placed along the third finger and the other along the radius in palpation contact.
• Perform wrist radial deviation.
• Assess the end feel.
• The normal radial deviation angle of approximately 25 degrees was measured with the fingers adducted with the palm flat on the table.

Wrist Ulnar Deviation

• Patient seated with the forearm in pronation resting on a table.
• The elbow flexed to 90 degrees, and the arm was slightly abducted.
• One goniometer arm is placed along the third finger and the other along the radius in palpation contact.
• Perform wrist ulnar deviation.
• Assess the end feel.
• The normal ulnar deviation angle of approximately 30 degrees was measured with the fingers adducted with the palm flat on the table.

Ligaments of the Wrist

The ligaments of the wrist can be divided into extrinsic and intrinsic ligaments. The extrinsic ligament connects the carpal bones to the radius or metacarpals. They can be further separated into volar and dorsal ligaments. The intrinsic ligament originates and inserts onto the different carpal bones (except there are no ligamentous connections between the lunate and capitate).

Wrist ligaments can also be grouped into the ligaments supporting each of the wrist joints:

• The distal radioulnar joint is supported by the volar and dorsal radioulnar ligaments.
• The radiocarpal joint is stabilised by the dorsal and the palmar radiocarpal ligaments, the palmar ulnocarpal ligaments, the ulnar collateral carpal ligament, and the radial collateral carpal ligament.
• The midcarpal joint is reinforced by the dorsal and palmar intercarpal ligaments and the deltoid ligament.

The tables below list the wrist ligaments supporting each joint.

Ligaments Supporting Distal Radioulnar Joint

Key ligaments	Origin	Insertion	Action/role	Key palpation points
Volar radioulnar ligament	Anterior margin of the ulnar notch at the distal radius	Anterior portion of the head of the ulna	Reinforces distal radioulnar joint Belongs to the triangular fibrocartilage complex (TFCC) and helps to support the triangular fibrocartilage disc, provides load-bearing, and helps to stabilise the ulnar side of the wrist	To palpate the head of the ulna move your fingers along the shaft of the ulna distally. The distal end of the ulna is the head of the ulna. You can also find the head of the ulna by first palpating the dorsal tubercle on the distal radius. Next, slide your fingers about two and a half centimetres laterally to locate the head of the ulna.
Dorsal radioulnar ligament	Posterior margin of the ulnar notch at the distal radius	Posterior portion of the head of the ulna

Ligaments Supporting Radiocarpal Joint

Key Ligaments	Origin	Insertion	Action/role	Key palpation points
Dorsal radiocarpal ligament (radiolunotriquetral ligament)	Dorsal radial tubercle at the distal end of radius	Triquetrum	Stabilises the radiocarpal joint Restricts full wrist flexion	First, locate the radial styloid process to palpate the dorsal tubercle' (Lister's tubercle). From the radial styloid process, move your fingers to the posterior aspect of the radius and feel for the bony ridge on the distal end of the radius. The dorsal tubercle is between the extensor pollicis longus tendons and the extensor carpi radialis brevis.
Palmar (Volar) radiocarpal ligaments: Radioscaphocapitate (RSC) ligament Long radiolunate (LRL) ligament Short radiolunate (SRL) ligament Radioscapholunate (RSL) ligament (ligament of Testut)	RSC: radial styloid process LRL: ulnar to the radioscaphocapitate ligament SRL: palmar to the lunate facet of the distal radius articular surface RSL: ulnar to the long radiolunate ligament	RSC: the radial aspect of the waist of the scaphoid LRL: radial half of the palmar surface of the lunate SRL: proximal margin of the palmar surface of the lunate RSL: merges with the scapholunate interosseous ligament. Note: It is not always considered a ‘true’ ligament as it includes branches of the radial artery and the neurovascular bundle.	Connect the radius to the carpal bones RSC: Primary stabilizer of the wrist Prevents ulnar drift	To palpate the radial styloid process, follow your fingers along the shaft of the radius to its lateral side. You will feel the bony projection on the lateral aspect of the radius, which is the most distal part of the radius. This is the radial styloid process.
Palmar (volar) ulnocarpal ligaments: Ulnolunate ligament Ulnocapitate ligament	Anterior margin of the triangular fibrocartilage complex The palmar radioulnar ligament	Capitate and lunate bones	Prevent palmar translocation of the ulnar carpal bones Allow radial deviation of the wrist. Limit the adduction and ulnar deviation of the wrist joint.
Ulnar collateral carpal ligament (Ulnotriquetral division of the palmar ulnocarpal ligament)	The end of the ulnar styloid process	Triquetrum		To palpate the ulnar styloid process, first locate the head of the ulna. Move your fingers towards the posterior medial aspect of the distal ulna to palpate the ulnar styloid process, which is the attachment site for the articular disc in the ulnar collateral ligament. To palpate the triquetrum, position the patient's hand with the ulnar side up. Place your finger on the ulnar side of the patient's hand, just above the ulnar styloid process. Ask the patient to deviate the wrist towards the radial side. The triquetrum bone will pop up under your finger.
Radial collateral carpal ligament (radioscaphoid ligament )	The radial styloid process	Distally at the radial surface of the scaphoid bone	Radial stabiliser of the wrist Limits abduction	The scaphoid bone can be palpated on the volar side. First, find the tubercle of the scaphoid in the thenar eminence. The tender spot on the thenar eminence is the tubercle. Turn the hand with the dorsal side up. Locate the snuff box by resisting thumb extension. You will see the snuff box at the base of the thumb. The rest of the scaphoid bone can be palpated inside the snuff box.

Ligaments Supporting Midcarpal Joint

Key ligaments	Origin	Insertion	Action/role	Key palpation points
Dorsal intercarpal ligaments	Dorsal tubercle of the triquetrum	The dorsal groove of the scaphoid bone The lunate bone The trapezium bone (in 50% of individuals)	Provides stability to the carpal bones, especially the stability of the scapholunate complex Prevents scapholunate dissociation during upper limb weight-bearing activities	See Bones and Articulations subheading for carpal bones palpation
Deltoid (arcuate) ligament: scaphocapitate ligament (SCL) triquetrohamocapitate ligament (THL)	Proximal carpal raw: scaphoid and triquetrum bones	Distal carpal raw: capitate and hamate bones	Midcarpal stabilising ligament
Palmar (volar) intercarpal ligaments	Palmar surface of the carpal bones	Adjacent carpal bones	Define the structure of the ligamentous palmar arch.

Wrist Retinacula

A band of thickened deep fascia around tendons is called a retinaculum. Its role is to hold the tendon in place. The wrist has two retinacula: flexor and extensor.

• Wrist flexor retinaculum is a fibrous band on the palmar side of the hand near the wrist. It arches over the wrist's carpal bones and forms the carpal tunnel.
  • Medial attachment: pisiform bone and the hook of the hamate.
  • Lateral attachment: the scaphoid's tubercle and the trapezium's crest.
  • Role: It serves as a pulley system for the carpal flexor muscles and stabilises the carpal system by supporting the transverse carpal arch.

• Extensor retinaculum is a fibrous, thickened band that holds the extensor tendons at the dorsum of the wrist. It is an oblique band that runs downwards and medially.
  • Medial attachment: the styloid process of the ulna, triquetral and pisiform bones.
  • Lateral attachment: the lower part of the anterior border of the radius
  • The extensor retinaculum is located superficial to the extensor tendons and is continuous with the volar carpal ligament.
  • Role: prevents bowstringing (failure of the finger to fully flex accompanied by pain and discomfort)

Muscles of the Wrist

The wrist muscles can be grouped into compartments or based on their wrist action.

The anterior compartment of the forearm has three layers: superficial, intermediate and deep. The superficial layer houses flexor carpi ulnaris, palmaris longus, flexor carpi radialis, pronator teres. Flexor digitorum superficialis is located in the intermediate layer. Deep layer contains flexor pollicis longus, flexor digitorum profundus and pronator quadratus.

The posterior compartment of the forearm is divided into a superficial and deep layer. The superficial layer includes the extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and anconeus. The supinator is the muscle from the deep layer of the posterior forearm.

The tables below present the wrist muscles according to their function:

Forearm Pronators

Muscle	Origin	Insertion	Innervation	Action
Pronator teres	Medial epicondyle of the humerus via the common flexor tendon The coronoid process of the ulna	The lateral surface of the radial shaft	Median nerve (C6-C7)	Elbow flexion Forearm pronation
Pronator quadratus	The oblique ridge of the ulnar shaft	The anterior surface of the radial shaft.	The anterior interosseous nerve	Pulls the distal end of the radius over the ulna, which results in the pronation of the radioulnar joint.
Brachioradialis	The lateral supracondylar ridge	The styloid process of the radius	Radial nerve (C5-C6)	Elbow flexor when the forearm is neutral Involved in pronation to neutral when the forearm is in supination

Forearm Supinators

Muscle	Origin	Insertion	Innervation	Action
Supinator	Supinator crest of the ulna The radial collateral ligament The annular ligament The lateral epicondyle of the humerus	Lateral surface of the radial shaft	Radial nerve (C5-C6)	Prime supinator of the forearm
Biceps brachii: Short head(SH) Long head(LH)	SH: the coracoid process of the scapula LH: the supraglenoid tubercle of the scapula	SH/LH: radial tuberosity	Musculocutaneous nerve	Flexes the elbow joint, particularly when the forearm is supinated. Assists with forearm supination
Brachioradialis	The lateral supracondylar ridge	The styloid process of the radius	Radial nerve (C5-C6)	Elbow flexor when the forearm is neutral Assist in supinating the forearm to neutral when the forearm is in pronation

Wrist Flexors

Muscle	Origin	Insertion	Innervation	Action
Flexor digitorum profundus	Ulnar shaft and the interosseous membrane	Distal phalanges of fingers two to five through four tendons	Median nerve (C7,8, T1) Ulnar nerve (C8, T1)	Fingers and wrist flexion
Flexor pollicis longus	The anterior surface of the shaft of the radius and the interosseous membrane	The distal phalanx of the thumb	Median nerve (C8, T1)	Weak wrist flexor in addition to flexing the thumb
Flexor digitorum superficialis humeroulnar head (HUH) radial head (RH)	HUH: medial epicondyle via the common flexor tendon and the coronoid process RH: radial tuberosity	The middle phalanges of fingers two to five via four tendons	Median nerve (C7-8, T1)	Wrist and fingers flexor
Flexor carpi radialis	The medial epicondyle of the humerus via the common flexor tendon	The bases of the second and third metacarpals	Median nerve (C6, C7)	Wrist flexion and radial deviation
Flexor carpi ulnaris	The medial epicondyle via the common flexor tendon The head of the ulna	The hamate and the base of the fifth metacarpal	Ulnar nerve (C7, C8)	Wrist flexion and ulnar deviation
Palmaris longus	The medial epicondyle via the common flexor tendon	The flexor retinaculum and palmar fascia	Median nerve (C8)	Weak wrist flexor Note: may be absent is some population

Wrist Extensors

Muscle	Origin	Insertion	Innervation	Action
Extensor carpi ulnaris	Lateral epicondyle of humerus via the common extensor tendon Posterior border of ulna	The base of the fifth metacarpal	Radial nerve (C7,8)	Wrist extension Wrist ulnar deviation
Extensor carpi radialis longus	Lateral supracondylar ridge of humerus	The base of the second metacarpal	Radial nerve (C6,7)	Wrist extension and radial deviation
Extensor carpi radialis brevis	Lateral epicondyle of humerus via common extensor tendon	Distal and middle phalanges of each finger	Radial nerve (C6,7)
Extensor digitorum	Lateral epicondyle via the common extensor tendon, and then splits into four tendons to insert into the extensor expansions of fingers two to five	Extensor expansions of fingers two to five via four tendons	Radial nerve (C7,8)	Weak wrist extensor

Wrist Ulnar Deviation

Muscle	Origin	Insertion	Innervation	Action
Flexor carpi ulnaris	The medial epicondyle via the common flexor tendon The head of the ulna	The hamate and the base of the fifth metacarpal	Ulnar nerve (C7, C8)	Wrist flexion and ulnar deviation
Extensor carpi ulnaris	Lateral epicondyle of humerus via the common extensor tendon Posterior border of ulna	The base of the fifth metacarpal	Radial nerve (C7,8)	Wrist extension Wrist ulnar deviation

Wrist Radial Deviation

Muscle	Origin	Insertion	Innervation	Action
Flexor carpi radialis	The medial epicondyle of the humerus via the common flexor tendon	The bases of the second and third metacarpals	Median nerve (C6, C7)	Wrist flexion and radial deviation
Extensor carpi radialis brevis	Lateral epicondyle of humerus via common extensor tendon	Distal and middle phalanges of each finger	Radial nerve (C6,7)	Wrist extension and radial deviation
Extensor carpi radialis longus	Lateral supracondylar ridge of humerus	The base of the second metacarpal	Radial nerve (C6,7)

Innervation of the Wrist

The wrist joints are supplied by branches of the anterior and posterior interosseous nerves, ulnar, median, and radial nerves according to the following distribution:

• The radiocarpal joint is supplied by branches of the anterior and posterior interosseous nerve
• The midcarpal and intercarpal joints are supplied anteriorly by the anterior interosseous, median, and ulnar nerves and by the deep branch of the ulnar nerve. The posterior interosseous nerve supplies the posterior aspects of the joints
• The distal radioulnar joint is innervated by the anterior interosseous nerve and the posterior interosseous nerve

Nerve	Origin	Branches	Motor fibres	Sensory fibres
Median nerve	Brachial plexus lateral and medial cords	Anterior interosseous	Pronator teres, flexor carpii radialis, palmares longus, flexor digitorum superficialis	The skin over the thenar eminence, palmar aspect of the thumb, index, middle finger and radial half of the ring finger
Ulnar nerve	Brachial plexus medial cord	Articular branches Muscular branches The palmar and dorsal cutaneous branches Terminal branches in the hand: superficial branch of ulnar nerve deep branch of ulnar nerve.	Flexor carpi ulnaris, ulnar half of flexor digitorum profundus	Cutaneous innervation to the medial forearm and medial wrist
Radial nerve	Brachial plexus posterior cord	Superficial branch: lateral branch medial branch Deep branch: posterior interosseous nerve Posterior brachial cutaneous nerve Inferior lateral brachial cutaneous nerve Posterior antebrachial cutaneous nerve Muscular branches	Extensor carpii radialis brevis, supinator, extensor digitorum, extensor digiti minimi , extensor carpii ulnaris, extensor pollicis longus, abductor pollicis longus, extensor indicis	Touch, pain and temperature sensations to portions of the back of the upper arm, forearm, the back of the hand and fingers

Vascular Supply of the Wrist

The vascular supply of the wrist is provided by four major vessels: the radial, ulnar, anterior interosseous, and posterior interosseous arteries. Their branches form anastomoses that create volar and dorsal arches at the wrist.

Artery	Origin	Branches	Supply
Radial artery	Terminal branch of brachial artery	Muscular branches Radial recurrent artery Palmar carpal branch Dorsal carpal branch Superficial palmar branch, Deep palmar branch, First dorsal metacarpal artery Princeps pollicis artery Radialis indicis artery	The elbow joint, lateral forearm muscles, radial nerve, carpal bones and joints, thumb, and lateral side of the index finger
Ulnar artery	Terminal branch of brachial artery	Anterior and posterior ulnar recurrent arteries Common interosseous artery Palmar carpal arch Superficial palmar arch Dorsal carpal branch	The elbow joint, medial and central forearm muscles, median and ulnar nerves, and common flexor sheath
Common interosseous artery	Branch of ulnar artery	Anterior and posterior interosseous arteries	Radius, ulna, deep flexors and extensors of forearm, median nerve, the interosseous membrane of the forearm, distal radioulnar joint, the skin of lateral margin of the forearm

Clinical Relevance

1. The distal radius fracture (Colles’ fracture) is one of the most common injuries of the upper limb, often as a result of the fall on an outstretched hand. It affects the distal radius and is characterised by the dorsal tilt, dorsal shift, radial tilt, radial shift, supination and impaction.
2. The scaphoid fractures symptom includes pain in the anatomical snuff box after a hyperextension trauma. Avascular necrosis and nonunion are the most common scaphoid fracture complications.
3. Carpal Instability can be classified into (1) proximal or distal carpal rows instability, or carpal instability dissociative (CID), (2) instability related to disturbed midcarpal joint kinematics, or carpal instability nondissociative (CIND).
4. Midcarpal instability can occur as a result of the injury to the ulnar arm of the arcuate ligament. Palmar midcarpal instability is a painful condition characterised by a snap during the ulnar deviation motion, known as the catchup clunk.
5. Allen's test assesses the circulation of the hand via superficial and deep palmar arches. During the test, the ulnar and radial arteries are compressed at the level of the proximal wrist crease. The result of compression is palmar blanching. Next, either the ulnar or radial artery is released from compression, which causes hyperaemia in the non-diseased state. Adequate collateral circulation is indicated by a return of colour to the hand within an adequate time period.

Resources

1. Special tests for the wrist exam
2. Watch this video for the palpation of the extensors and flexors of the wrist: