Wrist and Hand

Original Editors - Rachael Lowe

Top Contributors - Kim Jackson, Rachael Lowe, Laura Ritchie, George Prudden and Cheryl Rentchler

Introduction

The upper limb has sacrificed locomotor function and stability for mobility, dexterity and precision.  The hand sits at the end of the upper limb and is a combination of complex joints whose function is to manipulate, grip and grasp- this is made possible by the opposing movement of the thumb.[1]  

Bony Anatomy

The hand and wrist have a total of 27 bones arranged to roll, spin and slide[2]; allowing the hand to explore and control the environment and objects. The hand is divided into three regions[3]:

  • Proximal region of the hand is the carpus (wrist)
  • The middle region the metacarpus (palm)
  • The distal region the phalanges (fingers).

The Carpus

The carpus consists of eight bones, sitting in two rows, with four bones in each row (figure 1).  The carpus controls length-tension relationships in the multiarticular hand muscles and to allow fine adjustment of grip.[4] 

Three of the bones in the proximal row articulate with the radius forming the radiocarpal joint and distally with the distal carpal forming the midcarpal joint.  The four carpal bones in the distal row articulate with the bases of the five metacarpal bones forming the carpometacarpal joints[5].  The joints formed between the carpal bones are known as the intercarpal joints and most are of the plane synovial type[1], as the bones interlock with each other the rows are sometimes referred to as two single synovial joints[1].   

Figure 1 - Bones of the Hands
Bones - Dorsum of Left hand - Gray's Anatomy
Bones - Dorsum of Left Hand
Bones - Volar of Left Hand - Gray's Anatomy
Bones - Volar of Left Hand

The arrangement of the bones and ligaments allows very little movement between bones[1], but they do slide contributing to the finer movements of the wrist[6].  The exception to this is the capitate which has a larger range of movement[1].  The small bones are named after the shape they resemble.

Proximal Row[5]

  • Scaphoid – (boat like)– anterior surface palpable tubercle. Articulates proximally with radius, medially with lunate and distally with the head of the capitate.  It is a common site of fracture- 70% of all carpal fractures[5], often injured by a fall onto an outstretched limb
  • Lunate – (moon shaped) – Its palmar surface is smooth and convex and is larger than its dorsal surface.  Proximally it articulates with the radius and articular disc, medially with the triquetrum, laterally with the scaphoid and distally with the head of the capitate
  • Triquetrum – (three cornered) – Nestles in the space between the lunate and hamate.  When the hand is adducted it enters the radiocarpal joint.
  • Pisiform – (pea shaped) = a small round bone found in the tendon of flexor carpi ulnaris.  It articulates with the palmar surface of the triquetrum.   The anterior surface projects distally and laterally forming the medial part of the carpal tunnel. 

Distal Row[5]

  • Trapezium – four sided figures with no two sides parallel – the most irregular, with a palpable tubercle and groove anterior medially. It articulates proximally with the scaphoid and medially with the trapezoid.  Its articular surface is saddle-shaped and contributes to the mobility of the carpometacarpal joint of the thumb
  • Trapezoid – four sided figure with two parallel sides – Articulates distally with the second metacarpal, laterally with the trapezium, proximally with the scaphoid and medially with the capitate
  • Capitate - head shaped – The largest of all the carpal bones sitting centrally and articulating with the lunate and scaphoid, medially with the hamate and laterally with the trapezoid.  The distal surface articulates mainly with the base of the third metacarpal but also by narrow surfaces with the bases of the second and fourth metacarpals.
  • Hamate – hooked – This is wedge shaped with a curved palpable hook projecting from the palmar surface near the base of the fifth metacarpal.

The following pneumonic makes it easy to remember the position of each bone:    

Carpal mneumonic
The Carpal Tunnel – formed by the anterior concave space formed by the pisiform and hamate – on the ulnar side and the scaphoid and trapezium – on the radial side, with a roof like covering of the flexor retinaculum (strong fibrous bands of connective tissue).  The long flexor tendons of the digits and thumb and the median nerve pass through the carpal tunnel

The Metacarpus

The metacarpus, the palm of the hand, which is made up of five bones – the metacarpals.  The bones are numbered laterally, from the thumb, 1 – 5.  Each bone is long with a proximal quadrilateral base, a shaft (body) and a distal rounded head.  The base of the first metacarpal is saddle-shaped and articulates with he trapezium.  The base of the second metacarpal articulates with the trapezium, trapezoid and capitate. The base of the third metacarpal articulates with the capitate.  The bases of the fourth and fifth metacarpal articulate with the hamate.  The bases of the second to fifth metacarpals also articulate with each other.

The heads of the metacarpals, commonly known as knuckles, are smooth and rounded and extend onto the palmar surface – these become visible when the fist is clenched[3].  The head of the first metacarpal is wider than the others, having two sesamoid bones, usually found in the short tendons crossing the joint, which articulate with the palmar part of the joint surface.  The heads fit into a concavity on the base of the proximal phalanx at the metacarapophlangeal joints.

The Phalanges

The phalanges, the fingers, consist of 14 long bones.  Apart from the thumb (the pollex) each phalanx has three bones, the distal, middle and proximal phalanx – the thumb has only two distal and proximal.  As with the metacarpals the phalanges are numbered 1-5 starting at the thumb.  The proximal phalanx is large and is concave for articulation with the head of the metacarpal.  The shaft is curved along its length being convex dorsally.  It is convex from side to side on its dorsal surface and flat on the palmar surface.  The distal end, the head, is smaller and convex to articulate with the next bone in sequence.  In order from the thumb digits are also known as the index finger, middle finger, ring finger and little finger.  

Joints of the Wrist and Hand

The wrist has two degrees of freedom[7], although some say three degrees of freedom because they include the movements of pronation and supination[4], which occur at the the radioulnar joint. The radioulnar joint is often referred to as a joint of the forearm but it is this articulation that gives the wrist more freedom of movement.  The true joints of the wrist and hand are listed in the table below[7].

Articulating surfaces /Joints of the wrist and hand
Joint Proximal articulation Distal Articulation Type Movement
Radiocarpal joint Radius and articular disc/ concave Scaphoid, lunate, triquetrum / – convex Ellipsoid Flexion-extension; Abduction-adduction
Midcarpal joint Scaphoid. Lunate, Triquetrum Trapezium, Trapezoid, Capitate, Hamate Gliding Flexion-extension; Abduction-adduction
Carpometacarpal joint (thumb) 1st metacarpal trapezium Saddle Flexion-extension; Abduction-adduction; circumduction; opposition
Carpometacarpal joint (fingers) 2nd metacarpal

3rd metacarpal

4th metacarpal

5th metacarpal

trapezoid, trapezium

capitate

capitate, hamate

hamate

Ellipsoidal Flexion-extension
Metacarpophalangeal joints Carpals phalangeal Ellipsoidal Flexion, extension, abduction, adduction, circumduction
Interphalangeal Distal phlangeal Proximal phalangeal Hinge Flexion (lots) Extension (minimal)

Ligaments of the Wrist and Hand

The stability of the wrist is provided by ligaments (see table); on the palmar aspect is the flexor retinaculum which together with the carpal bones forms a canal – the carpal tunnel - which nerves, muscles and blood vessels run through, it is this area that is involved in carpal tunnel syndrome.

Ligaments of the Wrist and Hand
Ligament Location Function
Posterior radiocarpal ligament runs diagonally across the posterior aspect of the wrist from the distal end of the radius to the triquetral and hamate carpal bones (on the ulnar side of the wrist limits flexion of the wrist
Anterior radiocarpal ligament runs from the anterior aspect of the distal end of the radius to the scaphoid, lunate and capitate bones of the wrist Limits extension of the wrist
Radial collateral ligament from the styloid process of radius to the scaphoid bone limits adduction of wrist (frontal plane)
Ulnar collateral ligament from the styloid process of the ulna to the triquetral limits abduction (front plane)
Anterior, posterior and interosseous carpal ligaments Between the carpal bones holds carpal bones together - reinforced by the shape and interlocking structure of the bones
Transverse carpal ligament flexor retinaculum The roof of the carpal tunnel which the median nerve and flexor tendons pass through
Ligaments of the fingers To be added

Movements of the Wrist and Hand

Movements of the Wrist[1]
Movement Muscles Range Origin Insertion Innervation Joint
Flexion Flexor carpi radialis 0-80 Medial Epicondyle of humerus 2nd and 3rd metacarpals Median nerve (C6,7) Radiocarpal Jt
Flexor carpi ulnaris Medial epicondyle of humerus and sup.post. border of ulna Pisiform, hamate and base 5th metacarpal Ulnar nerve (C7,8)
Palmaris longus Medial epicondyle of humerus Flexor reinaculum and palmar aponeurosis Median nerve (C8)
Flexor digitorum superficialis Medial epicondyle of humerus, coronoid process of

ulna, and a ridge along lateral margin of anterior surface of radius

Middle phalanges of each finger Median nerve (C7,8 T1)
Flexor digitorum profundus Anterior medial surface of body of ulna Base of distal phalanx of thumb Median nerve (C7,8, T1)

Ulnar nerve (C8, T1)

Flexor pollicis longus Anterior surface of radius and interosseous membrane Base of distal phalanx of thumb Median nerve (C8, T1)
Extension Extensor carpi radialis longus 0-70 Lateral supracondylar ridge of humerus 2nd metacarpal Radial nerve (C6,7) Radiocarpal Jt
Extensor carpi radialis brevis Lateral epicondyle of humerus Distal and middle phalanges of each finger Radial nerve (C6,7)
Extensor carpi ulnaris Lateral epicondyle of humerus and posterior border of ulna 5th metacarpal Radial nerve (C7,8)
Extensor digitorum Lateral epicondyle of humerus Distal and middle phalanges of each finger Radial nerve (C7,8)
Extensor indicis Posterior surface of ulna Tendon of extensor digitorum of index finger Radial nerve (C7, 8)
Extensor digiti minimi Lateral epicondyle of humerus Tendon of extensor digitorum on 5th phalanx Radial nerve (C7,8)
Extensor pollicis longus Posterior surface of middle of radius and ulna and interosseous membrane 1st metacarpal Radial nerve (C7,8)
Extensor pollicis brevis Posterior surface of middle of radius Base of proximal phalanx of thumb Radial nerve (C7,8)
Radial deviation Flexor carpi radialias 30 Medial Epicondyle of humerus 2nd and 3rd metacarpals Median nerve (C6,7) Radiocarpal Jt
Ulnar deviation Flexor carpi ulnaris 20 Medial epicondyle of humerus and sup.post. border of ulna Pisiform, hamate and base 5th metacarpal Ulnar nerve (C7,8) Radiocarpal Jt
Supination

(of forearm)

Supinator 60 Lateral epicondyle of humerus and ridge near radial notch of ulna Lateral surface of proximal one-third of radius Radial nerve (C5,6) Sup. and inf.radioulnar jt
Biceps brachii Long head - supraglenoid tubercle; Short head - coracoid process of scapula Radial tuberosity and bicipital aponeurosis Musculocutaneous nerve (C5,6)
Brachioradialis Medial and lateral borders of distal end of humerus Superior to styloid process of radius Radial Nerve (C5,6)
Pronation

(of forearm)

Pronator teres 40 Medial epicondyle of humerus and coronoid process of ulna Midlateral surface of radius Median nerve (C6,7) Sup.and inf.radioulnar jt
Pronator quadratus Distal portion of shaft of ulna Distal portion of shaft of radius Median nerve (C8, T1)
Brachioradialis Medial and lateral borders of distal end of humerus Superior to styloid process of radius Radial nerve (C5,6)

Arches of the Hand

The hand, when in at rest, forms a hollow at the palm, with the fingers flexed and the thumb in slight opposition. There are three distinct arches, longitudinal, oblique and transverse, that are formed by the bones, ligaments and tendons these are of vital importance when gripping and manipulating objects.

128px-Hand-arches.svg.pngLongitudinal Arches (Brown)

These are known as the carpometacarpophalangeal arches run from the wrist to each digit. The arches are concave with the keystone laying level with the metacarpophalangeal joint; muscular imbalance at this point can decrease the concavity of the arch. The most important of these arches are the ones of the index finger and middles finger which are used when gripping objects, especially the arch formed to the index finger which we use when holding and using objects such as a pen.

Oblique Arch (Red)

These arch runs from the base of the hypothenar eminence to the head of the second metacarpal. It lies in parallel the palmar crease 'life line' and is evident when holding tools or a tennis raquet.

Transverse Arches (Light green and Dark Green)

This arches lays across the palm and is maintained by the retinaculum. It runs from the wrist where its shape is maintained by the retinaculum and therefore more rigid, distally to the metacarpals heads where it is much shallower and more flexible.

Clinical Examination

Conditions

Procedures

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 Palastanga N, Soames R. Anatomy and Human Movement: Structure and Function. 6th Ed. London: Churchill Livingstone, 2012.
  2. Maitland, G.D. Maitland's Peripheral Manipulations. 3rd Edition Edinburg: Elsevier Butterworth-Heinemann, 1999.
  3. 3.0 3.1 Physical Examination of the Spine and Extremities. Hoppenfield, S. New York: Appleton-Century-Crofts, 1976.
  4. 4.0 4.1 Levangie PK, Norkin CC. Joint Structure and Function: A Comprehensive Analysis. 5th Ed. Philadelphia: F A Davis Company, 2011
  5. 5.0 5.1 5.2 5.3 Principles of Anatomy & Physiology. Tortora GJ, Derrickson B. 13th Ed. NJ: John Wiley & Sons, Inc, 2012.
  6. Cael C. Functional Anatomy: Musculoskeletal Anatomy, Kinesiology, an Palpation for Manual Therapists. Lippincott Williams & Wilkins, 2009.
  7. 7.0 7.1 Kapandji I.A. The Physiology of the Joints: Volume 1, The Upper Limb. 5th Ed. London: Churchill Livingstone, 1982.