Functional Anatomy of the Wrist

Original Editor - Ewa Jaraczewska

Top Contributors - Ewa Jaraczewska, Jess Bell and Kim Jackson  

Introduction

The wrist includes three joints: the distal radioulnar joint, the radiocarpal joint and the midcarpal joint. The movements at the wrist are flexion and extension, radial and ulnar deviation and pronation and supination (at the distal radioulnar joint). Optimal wrist function requires adequate range of motion. Wrist motion is controlled by the ligaments and the proximal forearm muscles. This article discusses the key anatomical structures of the wrist which enable functional movement, 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 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 consists of three joints:

• Distal radioulnar joint - made up of the distal ulna and distal radius
• Radiocarpal joint - made up of the scaphoid, lunate, and triquetrum (proximal carpal bones) and the distal radius
  • Please note that the pisiform (the fourth bone in the proximal row of carpal bones) sits on top of the triquetrum, so it is not part of the radiocarpal joint
• Midcarpal joint - trapezium, trapezoid, capitate, and hamate bones (distal carpal bones) and the proximal carpal bones (scaphoid, lunate, and triquetrum)

Distal Ulna

Includes the ulnar head and styloid process.

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

Distal Radius

• Four articular surfaces:
  • Anterior surface: concave
  • Medial surface: concave ulnar notch (holds the head of the ulna in place)
  • Lateral surface: radial styloid process
  • Inferior surface: has two facets which articulate with the scaphoid and the lunate
• Dorsal tubercle (known as Lister's tubercle) is located on the posterior surface

Carpal Bones

Proximal row:

• Scaphoid (navicular): most lateral bone of the proximal row. The palmar surface contains the scaphoid tubercle and the floor of the anatomical snuffbox.
• Lunate: articulates with the scaphoid on its lateral side and the triquetrum on its medial side.
• Triquetrum: other names include triquetral, triangular, or cuneiform bone. It is a triangular / pyramidal-shaped bone located on the medial side of the wrist. It has multiple articular surfaces: the lunate articulates on its lateral side, the pisiform on its anterior side and the hamate on its distal side.
• Pisiform: the smallest carpal bone which only articulates with the triquetrum, and does not form part of the wrist joint.

Distal row:

• Trapezium: located on the radial side of the distal row of the carpal bones. It has four articulations for the first metacarpal, second metacarpal, scaphoid and trapezoid bones. The articulation between the trapezium and first metacarpal provides significant mobility in the hand, enabling thumb opposition.
• Trapezoid: also known as the lesser multangular bone. This is the smallest bone of the distal row of the carpal bones. It gives structure to the palm.
• Capitate: the largest and most central carpal bone. It articulates with the bases of the second and third metacarpal bones, forming part of the common carpometacarpal joint in the hand. In addition, it articulates with the scaphoid and lunate on its proximal surface, the trapezoid on its lateral surface, and the hamate on its medial surface.
• Hamate: sits on the medial side of the distal row of carpal bones. The hook of the hamate is a bony process extending from the palmar surface. This bone forms the medial border of the carpal tunnel.

Bones, Articulations and Kinematics of the Wrist

Wrist mobility depends on the interaction between the carpal bones and the radius. The ulna and the pisiform are not included, as the pisiform is a sesamoid bone, and the ulna is separated from the carpal bones by the articular disc. Each carpal bone has a separate motion axis. However, their movement depends on the alignment of the carpal bones with the distal radius.

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

The following theories have been used to describe wrist biomechanics:

• Row theory: the carpal bones are grouped into proximal and distal rows
• Column theory: the carpal bones are grouped into columns. The central column includes the lunate, capitate, and hamate. The lateral column (described as the mobile column) consists of the scaphoid, trapezium, and trapezoid. The medial column (rotation column) includes the triquetrum and pisiform.
• Row-column-theory: described as the modified column-theory. In this theory, the trapezium and trapezoid are included in the central column, and the pisiform has been eliminated from the medial column.
• Ring model: the wrist has two mobile links. These are the mobile trapezioscaphoid articulation and the rotatory triquetrohamate joint.
• Link joint-theory: in this theory, the radius, proximal row and distal row make up the individual links.
• Clamp theory: the bones are "clamped" into masses. The scaphoid bone is one mass, the lunate and triquetrum are the second mass, and the hamate, capitate, and trapezoid are the distal mass.

Bones and Articulations

Bones	Articulations	Characteristics	Key palpation points
Distal ulna Distal radius	Distal radioulnar joint	Essential for forearm rotation. If forearm supination and pronation are lost, upper limb function is significantly affected.
Proximal articulation: distal radius articular disc Distal articulation: scaphoid lunate triquetrum	Radiocarpal	A major synovial joint of the wrist. It contains the concave surface of the distal end of the radius, the articular disc of the distal radioulnar joint, and the convex surface of the proximal carpal row. The combined motion of the 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 can be palpated on the wrist's volar (palmar) side in the thenar eminence - this might feel tender for patients. You can palpate the rest of the scaphoid in the anatomical snuffbox. The snuffbox is on the dorsal surface of the hand. You can locate it by asking the patient to resist thumb extension. 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 their 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	The articulations between the proximal and distal carpal rows. Midcarpal motion includes the combined motion of three types of joint systems: between the scaphoid and the distal row between the lunate, triquetrum and the distal row between the intercarpal joints of the proximal row	To locate the trapezium, place your finger on your patient's thumb and slide it down to the first metacarpal. You will palpate a small indentation just below the first metacarpal. This is the trapezium. The trapezoid bone is located between the trapezium and the capitate. To find the capitate, slide your finger down the patient's middle finger to reach the third metacarpal bone. You have located the capitate when your finger drops into a divot (indentation). To palpate the hamate, 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 in the hypothenar eminence. The hook of the hamate is tender, and even gentle compression may be unpleasant for the patient.

Wrist Kinematics

Wrist movement is essential for many activities of daily living. For example:

• pouring water from a jug into a cup: requires a stable wrist in the sagittal and coronal planes and the ability to perform pronation/supination.
• 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 and a challenging / stable volar grip.
• zipping and unzipping a jacket: wrist must be able to adopt a flexed position, with the rest of the motion coming from the elbow and shoulder.
• lifting a laden (heavy) plate: requires forearm pronation/supination until contact is made with an extension grip on the plate. The wrist must be maintained in a stable position in all three planes until the 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	Sagittal 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 radial deviation	Neutral with a small degree of ulnar deviation
Midcarpal	Synovial joint-gliding joint	Sagittal 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

Please note that when discussing wrist movements, ulnar deviation = wrist adduction, and radial deviation = wrist abduction.

Wrist Passive Range of Motion Assessment

Wrist Flexion

• Patient is sitting with their upper arm supported on the table and their wrist off the table.
• The patient's elbow is in extension.
• Place the distal (moving) arm of the goniometer along the third metacarpal. The proximal (stationary) arm of the goniometer is held along the dorsal aspect of the distal forearm.
• Passively move the patient's wrist into flexion.
• Assess the end feel.
• Normal passive flexion of the wrist is approximately 80 degrees.

Wrist Extension

• Patient is sitting with their upper arm supported on the table and their wrist off the table.
• The patient's elbow is in extension.
• Place the distal (moving) arm of the goniometer along the third metacarpal. The proximal (stationary) arm of the goniometer is held along the dorsal aspect of the distal forearm.
• Passively move the patient's wrist into extension.
• Assess the end feel.
• Normal passive extension of the wrist is approximately 65 degrees.

Wrist Radial Deviation

• Patient is sitting with their forearm in pronation, resting on a table.
• Their elbow is flexed to 90 degrees, and their arm is slightly abducted.
• The distal (moving) goniometer arm is placed along the third finger and the proximal (stationary) along the radius.
• Passively move the patient's wrist into radial deviation.
• Assess the end feel.
• Normal passive radial deviation is approximately 25 degrees when measured with the fingers adducted and the palm flat on the table.

Wrist Ulnar Deviation

• Patient is sitting with their forearm in pronation, resting on a table.
• Their elbow is flexed to 90 degrees, and their arm is slightly abducted.
• The distal (moving) goniometer arm is placed along the third finger and the proximal (stationary) along the radius.
• Passively move the patient's wrist into ulnar deviation.
• Assess the end feel.
• Normal passive ulnar deviation is approximately 30 degrees when measured with the fingers adducted and 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 ligaments connect the carpal bones to the radius or metacarpals. They can be further separated into volar (palmar) and dorsal ligaments. The intrinsic ligaments originate and insert onto the different carpal bones (please note, there are no ligamentous connections between the lunate and capitate).

The wrist ligaments can also be grouped in terms of 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, 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 the 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 the distal radioulnar joint Belongs to the triangular fibrocartilage complex (TFCC) and helps 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 head of the ulnar forms the distal end of the ulna. You can also find the head of the ulna by palpating the dorsal tubercle on the distal radius. Next, slide your fingers about 2.5cm 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 the Radiocarpal Joint

Key Ligaments	Origin	Insertion	Action/role	Key palpation points
Dorsal radiocarpal ligament (radiolunotriquetral ligament)	Dorsal radial tubercle at the distal end of the radius	Triquetrum	Stabilises the radiocarpal joint. Restricts full wrist flexion	To palpate the dorsal tubercle (Lister's tubercle), first locate the radial styloid process. 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: the RSL 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 stabiliser 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 a 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 Ulnotriquetral ligament	Anterior margin of the triangular fibrocartilage complex, the palmar radioulnar ligament and ulnar styloid process	The palmar aspects of the lunate, capitate, and triquetrum	Prevent palmar translocation of the ulnar carpal bones. Allow radial deviation of the wrist. Limit ulnar deviation of the wrist joint.	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. This 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 their wrist towards the radial side. The triquetrum bone will pop up under your finger.
Radial collateral carpal ligament (radioscaphoid ligament )	Radial styloid process	Distally at the radial surface of the scaphoid bone	Radial stabiliser of the wrist. Limits radial deviation.	The scaphoid can be palpated on the volar (palmar) side of the wrist in the thenar eminence - this might feel tender for patients. You can palpate the rest of the scaphoid in the anatomical snuffbox. The snuffbox is on the dorsal surface of the hand. You can locate it by asking the patient to resist thumb extension.

Ligaments Supporting the Midcarpal Joint

Key ligaments	Origin	Insertion	Action/role	Key palpation points
Dorsal intercarpal ligament	Dorsal tubercle of the triquetrum	Dorsal groove of the scaphoid, the lunate and the trapezium (in 50% of individuals)	Provides stability to the carpal bones, especially to 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 row: scaphoid and triquetrum	Distal carpal row: capitate and hamate	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 tendons in place. The wrist has two retinacula:

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

• Extensor retinaculum: 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, triquetrum and pisiform.
  • Lateral attachment: the lower part of the anterior border of the radius.
  • The extensor retinaculum is located superficially to the extensor tendons and is continuous with the volar carpal ligament.
  • Role: prevents bowstringing (failure of the finger to fully flex, which is 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 layer: houses flexor carpi ulnaris, palmaris longus, flexor carpi radialis, pronator teres
• intermediate layer: houses flexor digitorum superficialis
• deep layer: contains flexor pollicis longus, flexor digitorum profundus and pronator quadratus

The posterior compartment of the forearm is divided into two layers:

• superficial layer includes the extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, anconeus, brachioradialis, extensor carpi radialis longus, and extensor carpi radialis brevis
• deep layer contains supinator, extensor pollicis longus, extensor pollicis brevis, abductor pollicis longus, and extensor indicis

The following tables below describe relevant muscles according to their action:

Forearm Pronators

Muscle	Origin	Insertion	Innervation	Action
Pronator teres	Medial epicondyle of the humerus via the common flexor tendon, coronoid process of the ulna	Lateral surface of the radial shaft	Median nerve (C6-C7)	Elbow flexion Forearm pronation
Pronator quadratus	Oblique ridge of the ulnar shaft	Anterior surface of the radial shaft	Anterior interosseous nerve	Pulls the distal end of the radius over the ulna, which results in pronation of the radioulnar joint
Brachioradialis	Lateral supracondylar ridge	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, radial collateral ligament, annular ligament, 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: coracoid process of the scapula LH: 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	Lteral supracondylar ridge	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)	Finger and wrist flexion
Flexor pollicis longus	Anterior surface of the shaft of the radius and the interosseous membrane	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	Middle phalanges of fingers two to five via four tendons	Median nerve (C7-8, T1)	Wrist and finger flexion
Flexor carpi radialis	Medial epicondyle of the humerus via the common flexor tendon	Bases of the second and third metacarpals	Median nerve (C6, C7)	Wrist flexion and radial deviation
Flexor carpi ulnaris	Medial epicondyle via the common flexor tendon, head of the ulna	Hamate and the base of the fifth metacarpal	Ulnar nerve (C7, C8)	Wrist flexion and ulnar deviation
Palmaris longus	Medial epicondyle via the common flexor tendon	Flexor retinaculum and palmar fascia	Median nerve (C8)	Weak wrist flexor Note: may be absent in some populations

Wrist Extensors

Muscle	Origin	Insertion	Innervation	Action
Extensor carpi ulnaris	Lateral epicondyle of humerus via the common extensor tendon, posterior border of ulna	Base of the fifth metacarpal	Radial nerve (C7,8)	Wrist extension and ulnar deviation
Extensor carpi radialis longus	Lateral supracondylar ridge of humerus	Base of the second metacarpal	Radial nerve (C6,7)	Wrist extension and radial deviation
Extensor carpi radialis brevis	Lateral epicondyle of humerus via the common extensor tendon	Base of the third metacarpal	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	Medial epicondyle via the common flexor tendon, head of the ulna	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	Base of the fifth metacarpal	Radial nerve (C7,8)	Wrist extension and ulnar deviation

Wrist Radial Deviation

Muscle	Origin	Insertion	Innervation	Action
Flexor carpi radialis	Medial epicondyle of the humerus via the common flexor tendon	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	Base of the third metacarpal	Radial nerve (C6,7)	Wrist extension and radial deviation
Extensor carpi radialis longus	Lateral supracondylar ridge of humerus	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:

• The radiocarpal joint is supplied by branches of the anterior and posterior interosseous nerves
• 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 and 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 Palmar and dorsal cutaneous branches Terminal branches in the hand: superficial branch of the ulnar nerve deep branch of the 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	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. Distal radius fracture is one of the most common injuries of the upper limb. It often occurs as a result of a fall on an outstretched hand (FOOSH). It affects the distal radius and is characterised by a dorsal tilt, dorsal shift, radial tilt, radial shift, supination and impaction. Find out more in the Management of Distal Radius Fractures Programme.
2. Scaphoid fractures are associated with pain in the anatomical snuffbox after a hyperextension trauma. Avascular necrosis and nonunion are the most common complications associated with scaphoid fractures.
3. Carpal instability can be classified into (1) instability of the proximal or distal carpal rows, or carpal instability dissociative (CID) and (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 ulnar deviation, which is known as the catch-up clunk.
5. Allen's test assesses the circulation of the hand via the superficial and deep palmar arches. During this test, the ulnar and radial arteries are compressed at the level of the proximal wrist crease. This causes 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 acceptable time period.

Resources

1. Special tests for the wrist exam
2. Watch this video to learn about the palpation of the extensor and flexor muscles of the wrist: