WRIST JOINT

 The wrist is composed of radiocarpal and intercarpal articulations with 15 bones, 17 joints, and an extensive ligament system.

The primary forearm bone of wrist is radius which articulates with the two proximal carpal bones.

Bones that make up the wrist joint are

• Distal ulna
• Distal radius
• Carpal bones

DISTAL ULNA

The ulna is not in direct contact with the carpal bones. A fibrocartilaginous disc separates the ulna from the carpal bones.

PARTS OF ULNA THAT ARTICULATE WITH CARPAL BONES

• The ulnar styloid process

It is a bony projection, easily palpated with the forearm pronated, on the

ulnar side of the wrist

• The fovea

It is a depression at the base of this styloid process and provides attachment

for the fibrocartilaginous disc.

• The pole.

It is a concave articular surface allowing ulnar articulation with the

fibrocartilaginous disc.

DISTAL RADIUS

The distal end of radius is important for precision of movement. The carpal bones are in direct contact with the radius through several surfaces.

DORSAL SURFACE

It has a palpable tubercle known as tubercle of radius, Lister’s tubercle or dorsal tubercle.

Covers 1/3^rd of the wrist width . it has groves on either side and serves as a pulley for the extensor pollicis longus tendon.

The dorsal tubercle’s pulley function serves to redirect the pull of the extensor pollicis longus.

RADIAL SURFACE

the radial surface of the radius is a distal projection called the radial styloid process. radial styloid processes serve as attachment sites for the radial carpal collateral ligaments

DISTAL SURFACE

On the lateral aspect of distal surface of radius is the articulating surface for the distal radioulnar joint (also called as sigmoid notch or ulnar notch) which articulates with the scaphoid and lunate carpal bones.

CARPAL BONES

There are eight carpal bones which are more or less cuboid-shaped in the wrist.

ARTICULATING SURFACE

They have articulating surfaces on their proximal, distal, medial, and lateral aspects with roughened surfaces on their volar and dorsal sides that provide attachment sites for the wrist ligaments.

The sole exception is the pisiform bone, which has only one articulating surface.

These eight carpal bones are arranged in two rows:

The proximal row

The carpal bones contain, laterally to medially, the scaphoid, lunate, triquetrum, and pisiform

The distal row

It contains, laterally to medially, the trapezium, trapezoid, capitate, and hamate.

CAPITATE BONE

a central position at the wrist (in line with the middle finger), the capitate bone (os magnum)

is best approached from the dorsum

 The axis of motion for ulnar and radial deviation goes through this bone in a dorsopalmar direction.

SCAPHOID BONE

The scaphoid (formerly known as the navicular) bone is palpated distally to the styloid process of the radius

 Ulnar abduction of the wrist causes the bone to become prominent to the palpating fingers, whereas radial abduction causes the bone to recede.

The scaphoid seems to extend across both rows of carpal bones, giving the impression that the proximal row curves around the capitate.

TRAPEZIUM

The trapezium is palpated proximally to the first carpometacarpal (CMC) joint of the thumb and distal to the identified scaphoid by passively flexing and extending the thumb to identify the joint margin

LUNATE

The lunate is palpated more easily if the capitate bone is located first. The capitate is palpated as the proximal bone making up the articulation with the third metacarpal. Once the capitate is identified, the lunate is immediately proximal to the capitate and in line with and distal to Lister’s tubercle. In normal subjects, the lunate becomes prominent to the palpating finger as the wrist is passively flexed and recedes as the wrist is passively extended. The lunate is the most frequently dislocated bone in the wrist.

PISIFORM

The pea-shaped bone palpated on the palmar side of the wrist near the ulnar border is the pisiform bone. This bone can be grasped and moved from side to side. Serving as the point of attachment for the flexor carpi ulnaris tendon, this moveable bone qualifies as a sesamoid bone.

TRAPEZOID/TRIQUETRIUM/HAMATE

These are more difficult to distinguish directly by palpation.

The hamate is located by palpating its hook. This protuberance lies at a 45° angle into the palm from the pisiform.

The triquetrum is under the pisiform and best palpated on the dorsal wrist with the wrist in radial abduction. It is palpated as a bony prominence just distal to the ulnar styloid process.

The trapezoid is the most difficult carpal bone to palpate. It lies distal to the scaphoid, medial to the trapezium, and lateral to the capitate.

JOINTS OF WRIST

The wrist is often collectively classified as an ellipsoidal joint with two degrees of freedom.

• Radiocarpal joint
• Midcarpal joint/ Intercarpal joint

RADIOCARPAL JOINT

ARTICULATION; The radiocarpal joint is formed by the biconcave distal end of the radius and the biconvex proximal articulating surfaces of the scaphoid and lunate bones.

The concave distal end of the radius and the articular disk articulating with the convex scaphoid, lunate, and triquetrum

 A triangular fibrocartilaginous disc attaches to the distal end of the radius and the styloid process of the ulna proximally while the apex of the disc attaches to the triquetrum distally. The disc binds the radius and ulna together and separates the distal radioulnar joint and the ulna from the radiocarpal joint.

TYPE OF JOINT; As a synovial joint, the radiocarpal joint is classified as a condyloid joint The radiocarpal joint is also classified as a biaxial joint,

MOTION AT RADIOCARPAL JOINT

The wrist motions of flexion (volar flexion), extension (hyperextension), radial deviation, and ulnar deviation occurs at the radiocarpal joint.

Wrist flexion, the carpals glide posteriorly on the radius and articular disk.

Wrist extension, they glide anteriorly.

Radial deviation, they glide in an ulnar direction.

Ulnar deviation, they glide in the opposite direction.

Circumduction, The radiocarpal joint also allows flexion and extension, and radial deviation and ulnar deviation. The combination of all four of these motions is called circumduction.

There is no rotation at the wrist

PLANE OF MOTION; The joint allows sagittal plane motions (flexion, extension, and hyperextension) and frontal plane motions (radial deviation and ulnar deviation) .

CLOSE PACK POSITION; Its close-packed position is in extension with radial deviation.

MIDCARPAL JOINT

ARTICULATION; The midcarpal joint is formed by the proximal and distal carpal rows.

The scaphoid articulates with the trapezium, trapezoid, and capitate.

The lunate articulates with the capitate.

The triquetrum articulates with the hamate.

MOTION OF MIDCARPAL JOINT

The wrist motions of flexion, extension, radialand ulnar deviation takes place at this joint.

TYPE OF JOINT; Plane joint

It is nonaxial joint that allows gliding motions that contribute little to wrist motion in assistance with radiocarpal joint motion

WRIST JOINT MOTION

Flexion and extension occur in the sagittal plane around the frontal axis.

FLEXION; 90 degrees

EXTENSION; 70 degrees

RADIAL DEVIATION; 25 degrees

ULNAR DEVIATION; 35 degrees

END FEEL; The end feel for all wrist motions, except radial deviation, is soft tissue stretch.

The end feel for radial deviation is bony, due to bony contact between the radial styloid process and the scaphoid  bone.

FLEXION

MUSCLES; flexor carpi radialis, palmaris longus and flexor carpi ulnaris

ASSISTING MUSCLES; The flexor digitorum superficialis and flexor digitorum profundus can assist with flexion at the wrist when the fingers are completely extended, but when the fingers are in flexion, these muscles cannot develop sufficient tension due to active insufficiency.

EXTENSION

MUSCLES; extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carpi ulnaris

ASSISTING MUSCLES; The posterior wrist muscles may also assist with extension, particularly when the fingers are in flexion. Included in this group are the extensor pollicis longus, extensor indicis, extensor digiti minimi, and extensor digitorum

RADIAL DEVIATION

MUSCLES; The flexor carpi radialis and extensor carpi radialis longus and brevis contract to produce radial deviation

ULNAR DEVIATION

MUSCLES; The flexor carpi ulnaris and extensor carpi ulnaris cause ulnar deviation.

MUSCLES OF WRIST

The flexors attach on the medial epicondyle, and the extensors attach on the lateral epicondyle.

The muscles of the wrist are listed as follows

ANTERIOR

• Flexor carpi ulnaris
• Flexor carpi radialis
• Palmaris longus

POSTERIOR

• Extensor carpi radialis longus
• Extensor carpi radialis brevis
• Extensor carpi ulnaris

FLEXOR CARPI ULNARIS

ORIGIN; Medial epicondyle of humerus. Posterior aspect of the proximal ulna

INSERTION; Pisiform, hamate and base of fifth metacarpal

ACTION

• Flexion of the wrist
• Adduction of the wrist, together with the extensor carpi ulnaris muscle
• Weak flexion of the elbow

NERVE SUPPLY; Ulnar nerve (C8, T1)

PALPATION; Anteromedial surface of the forearm, a few inches below the medial epicondyle of the humerus to just proximal to the wrist, with resisted flexion/ adduction.

APPLICATION; The flexor carpi ulnaris is very important in wrist flexion or curling activities. In addition, it is one of only two muscles involved in wrist adduction or ulnar flexion.

STRENGHTENING; strengthened with any type of wrist-curling activity against resistance

FLEXIBILITY; To stretch the flexor carpi ulnaris, the elbow must be fully extended with the forearm supinated while a partner passively extends and abducts the wrist.

FLEXOR CARPI RADIALIS

ORIGIN; Medial epicondyle of the humerus

INSERTION; Base of the second and third metacarpals, anteriorly

ACTION;

• Flexion of the wrist
• Abduction of the wrist
• Weak flexion of the elbow
• Weak pronation of the forearm

NERVE SUPPLY; Median nerve (C6, C7)

PALPATION; Anterior surface of the distal forearm and wrist, slightly lateral, in line with the second and third metacarpals with resisted flexion and abduction

APPLICATION; The flexor carpi radialis, flexor carpi ulnaris, and palmaris longus are the most powerful of the wrist flexors. They are brought into play during any activity that requires wrist curling or stabilization of the wrist against resistance, particularly if the forearm is supinated

STRENGHTENING; The flexor carpi radialis may be developed by performing wrist curls against a handheld resistance. This may be accomplished when the supinated forearm is supported by a table, with the hand and wrist hanging over the edge to allow full range of motion. The extended wrist is then flexed or curled up to strengthen this muscle.

FLEXIBILITY; To stretch the flexor carpi radialis, the elbow must be fully extended with the forearm supinated while a partner passively extends and adducts the wrist.

PALMARIS LONGUS

ORIGIN; Medial epicondyle of the humerus

INSERTION; Palmar aponeurosis of the second, third, fourth, and fifth metacarpals

ACTION;

• Flexion of the wrist
• Weak flexion of the elbow

NERVE SUPPLY; Median nerve (C6, C7)

PALPATION; The palmaris longus is absent mostly however if present it is palpated from Anteromedial and central aspect of the anterior forearm is just proximal to the wrist, particularly with slight wrist flexion and opposition of thumb to the fifth finger. This opposition makes the tendon, when present, easily viewable.

APPLICATION; The palmaris longus is involved only in wrist flexion from the anatomical position because of its central location on the anterior forearm and wrist. It can, however, assist in abducting the wrist from an extremely adducted position back to neutral, and assist in adducting the wrist from an extremely abducted position back to neutral. It may also assist slightly in forearm pronation because of its slightly lateral insertion in relation to its origin on the medial epicondyle.

STRENGHTENING; strengthened with any type of wrist-curling activity,

FLEXIBILITY; Maximal elbow and wrist extension stretches the palmaris longus

EXTENSOR CARPI RADIALIS LONGUS

ORIGIN; Distal third of lateral supracondylar ridge of the humerus and lateral epicondyle of the humerus

INSERTION; Base of the second metacarpal (dorsal surface)

ACTION;

• Extension of the wrist
• Abduction of the wrist
• Weak flexion of the elbow
• Weak pronation to neutral from a fully supinated position

NERVE SUPPLY; Radial nerve (C6, C7)

PALPATION; Just proximal to the dorsal aspect of the wrist and approximately 1 cm medial to the radial styloid process, the tendon may be felt during extension and traced to the base of the second metacarpal, particularly when making a fist; proximally and posteriorly, just medial to the bulk of the brachioradialis

APPLICATION; The extensor carpi radialis longus, like the extensor carpi radialis brevis, is important in any sports activity that requires powerful wrist extension. In addition, both muscles are involved in abduction of the wrist

STRENGHTENING; The extensor carpi radialis longus may be developed by performing wrist extension against a handheld resistance. This may be accomplished with the pronated forearm being supported by a table with the hand hanging over the edge to allow full range of motion. The wrist is then moved from the fully flexed position to the fully extended position against the resistance.

FLEXIBILITY; The extensor carpi radialis longus requires the elbow to be extended with the forearm pronated while the wrist is passively flexed and slightly abducted.

EXTENSOR CARPI RADIALIS BREVIS

ORIGIN; Lateral epicondyle of the humerus

INSERTION; Base of the third metacarpal (dorsal surface)

ACTION;

• Extension of the wrist
• Abduction of the wrist
• Weak flexion of the elbow

NERVESUPPLY; Radial nerve (C6, C7)

PALPATION; Just proximal to the dorsal aspect of the wrist and approximately 1 cm medial to the radial styloid process, the tendon may be felt during extension and traced to the base of the third metacarpal, particularly when making a fist

APPLICATION; The extensor carpi radialis brevis is important in any sports activity that requires powerful wrist extension, such as golf or tennis.

STRENGHTENING; Wrist extension exercises, such as those described for the extensor carpi ulnaris, are appropriate for development of the muscle.

FLEXIBILITY; Stretching the extensor carpi radialis brevis and longus requires the elbow to be extended with the forearm pronated while the wrist is passively flexed and slightly adducted.

EXTENSOR CARPI ULNARIS

ORIGIN; Lateral epicondyle of the humerus. Middle two-fourths of the posterior border of the ulna

INSERTION; Base of the fifth metacarpal (dorsal surface)

ACTION;

• Extension of the wrist
• Adduction of the wrist together with the flexor carpi ulnaris muscle
• Weak extension of the elbow

NERVE SUPPLY; Radial nerve, posterior interosseous branch (C6–C8)

PALPATION; Just lateral to the ulnar styloid process and crossing the posteromedial wrist, particularly with wrist extension/adduction

APPLICATION; The extensor carpi ulnaris is the strongest muscle involved in wrist abduction and ulnar deviation. It acts as antagonist to wrist flexion to allow the finger flexors to function more effectively in gripping. Any activity requiring wrist extension or stabilization of the wrist against resistance, particularly if the forearm is pronated, depends greatly on the strength of this muscle along with the extensor carpi radialis brevis, and the extensor carpi radialis longus. They are often brought into play with the backhand in racquet sports.

STRENGHTENING; The extensor carpi ulnaris may be developed by performing wrist extension against a handheld resistance. This may be accomplished with the pronated forearm being supported by a table with the hand hanging over the edge to allow full range of motion. The wrist is then moved from the fully flexed position to the fully extended position against the resistance.

FLEXIBILYTY; Stretching the extensor carpi ulnaris requires the elbow to be extended with the forearm pronated while the wrist is passively flexed and slightly abducted