Bones, Joints, and Muscles of the Forearm, Wrist, and Hand

Terminology• The wrist/hand region consists of 29 bones and

multiple joints - which lends to high mobility.• Wrist:

– As a joint, it is the articulation between the forearm and hand.

– Sometimes, the wrist is discussed as a region, which would include the carpal bones.

• Hand– The bones distal to the wrist joint.– As a region, the wrist is part of the hand.

Bones

• 29 bones including:–(2 from the forearm, 27 from the hand)

–Distal aspect of the radius and ulna

–8 carpal (bulk of the hand)

–14 phalanges (the fingers)

–5 metacarpals

–Total: 2+8+14+5=29

Bones• Radius and Ulna

–The radius is more massive distally than the ulna

–The ulna is more massive proximally than the radius

–Remember, forearm pronation and supination are the result of the radius rotating about the ulna

• Carpal Bones

–8 total

–2 rows of 4

–Proximal row:

•pisiform, triquetrum, lunate, scaphoid

–Distal row:

•hamate, capitate, trapezoid, trapezium

Bones - Metacarpals & Phalanges

5 Metacarpals

1

2 3 4 5 Phalanges : proximal

middle

distal

ProximalDistal

Base

Shaft

Head

Radiocarpal Joint (wrist joint)

Type: Synovial Condyloid

Articular Surfaces:

Radius (distal end)

Prox. Row Carpal Bones

Allows for:• flexion •extension •adduction (ulnar deviation)•Abduction (radial deviation)

Motion - Wrist Joint

Abduction (radial deviation)

Adduction (ulnar deviation)

And of course, circumduction

Motions of the Phalanges

Flexion

Extension

Abduction Adduction

+Circumduction

Thumb Motion

Abduction / Adduction sagittal plane

Flexion / Extension

frontal planeOpposition

Forearm Pronators and Supinators

Supinators:

• Biceps Brachii

• Supinator

• Brachioradialis

Pronators:

• Pronator Teres

• Pronator Quadratus

• Brachioradialis

O: Medial Epicondyle of Humerus

I: Medial and Lateral Surface of Radius

A: Pronation of Radioulnar Joint

Integrated Function: Assists in deceleration of supination of radioulnar joint

Assists in dynamic stabilization of radioulnar joint

Pronator Teres

Pronator Quadratus

O: Distal anterior ulna

I: Distal anterior radius

A: Forearm Pronation

Integrated Function: Assists in deceleration of supination of radioulnar joint

SupinatorO: Lateral Epicondyle of

Humerus

I: Wraps around proximal radius

A: Supination of Radioulnar Joint

Integrated Function: Assists in deceleration of pronation of radioulnar joint

Assists in dynamic stabilization of radioulnar joint

Superficial Forearm Pronator and Wrist Flexors

• Pronator Teres

• Flexor Carpi Radialis

• Palmaris Longus

• Flexor Carpi Ulnaris

Muscles Causing Wrist Actions

• Wrist flexors– Flexor Carpi Radialis

– Flexor Carpi Ulnaris

– Palmaris Longus

• Wrist extensors– Extensor Carpi Radialis Longus

– Extensor Carpi Radialis Brevis

– Extensor Carpi Ulnaris

These muscles do not cause finger movements

Phalange Muscles• Finger flexors

– Flexor Digitorum Superficialis– Flexor Digitorum Profundus

• Thumb flexor– Flexor Pollicis Longus

• Finger extensors– Extensor Digitorum– Extensor Indicis– Extensor Digiti Minimi

• Thumb extensor– Extensor Pollicis Longus– Extensor Pollicis Brevis

These muscles assist inwrist actions

Attachments• Wrist Flexors

– All originate from the medial epicondyle of the humerus

– Insertions: anterior aspect of the wrist and hand

• Wrist Extensors

– All originate from the lateral epicondyle of the humerus

– Insertions: posterior aspect of wrist and hand

Attachments

• Wrist Abductors– Origin: anterior or posterior aspect of

forearm

– Insertion: radial side of hand

• Wrist Adductors– Origin: anterior or posterior aspect of

forearm

– Insertion: ulnar side of hand

Flexor Carpi Radialis

O: Medial Epicondyle of Humerus

I: Bases of 2nd and 3rd metacarpals

A: Flexion and Abduction of wrist (radial deviation)

Flexor Carpi Ulnaris O:Medial

Epicondyle of Humerus

I: Pisiform

A: Flexion and Adduction of Wrist (ulnar deviation)

Palmaris Longus Absent in 15 - 20% of Population

O: Medial Epicondyle of Humerus

I: Palmar Aponeurosis

A: Wrist flexion

Q: How do you test for this muscle and why is it important?

Palmaris Longus

Tested:

• With wrist slightly flexed

• Oppose thumb and little finger

Importance:

Used in tendon transfers (autografts)

Flexor Digitorum Superficialis

O: Medial Epicondyle of Humerus

I: 2nd through 5th Phalanges

A: Finger Flexion and Wrist Flexion

Integrated Function of Wrist Flexors

• Assists in deceleration of wrist extensors

• Assists in dynamic stabilization of the wrist and hand

• Flexor Carpi Radialis and Flexor Carpi Ulnaris:– Assists in deceleration of wrist abdution

• Flexor Digitorum Superficialis:– Assists in deceleration of finger extension

Extensor Carpi Radialis Brevis

O: Lateral Epicondyle of Humerus

I: Base of 3rd metacarpal on dorsal surface

A: Extension of wrist

Abduction of Wrist

Extensor Carpi Radialis Longus

O: Lateral Epicondyle of Humerus

I: Base of 2nd metacarpal

A: Extension of wrist

Abduction of wrist

(radial deviation)

Extensor Carpi UlnarisO: Lateral Epicondyle

of Humerus

I: Base of 5th metacarpal on dorsal surface

A: Extension of Wrist

Adduction of Wrist (ulnar deviation)

Integrated Function of Wrist Extensors• Assists in deceleration of wrist flexion

• Assists in dynamic stabilization of the wrist and hand

• Extensor Carpi Radialis Brevis and Longus:– Assists in deceleration of wrist adduction

• Extensor Carpi Ulnaris:– Assists in deceleration of wrist abduction

Nerves• Three primary nerves of the wrist and hand:

– Radial Nerve

• Innervates the triceps brachii and provides sensation to dorsal side of thumb, index, middle, and half of ring finger

– Ulnar Nerve

• Palmar side of the little finger and half of the ring finger

– Median Nerve

• Palmar side of thumb, index , and half of ring finger

Common Medical Conditions• Fractures, strains, sprains, dislocations

– Scaphoid bone is most frequently fractured carpal bone

– “Hook” of the Hamate fracture

Common Medical Conditions• Boutonniere Deformity and Mallet Finger

– Caused by the rupture of the extensor tendon

Carpal Tunnel Syndrome

• A disorder that causes numbness in the hand and pain in the wrist due to the compression of the median nerve

Carpal Tunnel Syndrome• Etiology:

– Short, repetitive movement, such as typing, knitting, and using vibrating tools for hours on end

– The lack of rest in between these motions irritates and inflames the flexor tendons that travel with the median nerve to the hand through an area in the wrist called the "carpal tunnel," which is surrounded by bones and a transverse ligament.

– The inflamed tendons squeeze the nerve against the ligament.

Carpal Tunnel Syndrome• The symptoms Include:

– Pain, numbness, or tingling in your hand and wrist, especially in the thumb and index and middle fingers; pain may radiate up into the forearm

– Increased pain with increased use of your hand, such as when you are driving or reading the newspaper

– Increased pain at night – Weak grip and tendency to drop objects held in the hand – Sensitivity to cold – Muscle deterioration especially in the thumb (in later

stages). • Treatment:

– Diagnosis by physician– Occupational Therapy/Physical Therapy

Prevention of Carpal Tunnel Syndrome• Ergonomics:

– Proper seating

– The height of your seat and the position of your backrest should be adjustable

– The chair should be on wheels so you can move it easily

– If you can adjust your table, set your waist angle at 90 degrees, then adjust your table so that your elbow makes a 90 degree angle when your hands are on the keyboard

Prevention of Carpal Tunnel SyndromeErgonomics:

– Elbow angle at 90 degrees. Try to hold your elbows close to your sides to help minimize "ulnar displacement" the sideways bending of the wrist (as when reaching for the "Z" key)

– Waist angle at 90 degrees

– With your elbows and waist at 90 degree angles, your feet should rest comfortably flat on the floor.

Carpal Tunnel Syndrome Exercises• Stretch the following muscles:

– Elbow Flexors– Wrist Flexors– Finger Flexors

• This will reduce the compression of the median nerve within the carpal tunnel

• EXTENSION EXERCISES ARE THE KEY TO RECOVERY• Strengthen the following muscles:

– Elbow Extensors– Wrist Extensors– Finger Extensors– Finger Abductors

• This will help hold the carpal tunnel open