Learning Outcomes: Students will be able to:

1. Describe the musculoskeletal anatomy of the forearm, wrist and hand and associated connective tissues that support these joints.
2. Articulate the functional design of the wrist and all hand joints and the osteokinematic and arthrokinematic movements possible at the joints.
3. Describe the origin, insertion, actions, and nerve innervation of the muscles that act on the radioulnar, wrist and hand joints.
4. Identify how to strengthen and stretch each of the muscles or muscle groups that act upon the wrist and hand joints.
5. Articulate the mechanisms that can contribute to pathology of the wrist and hand structures.
6. Identify the various unique structures and configurations of the hand that enable the human to grasp and use tools.

1. Proximal Transverse Arch: runs transversely and is formed by the two rows of the carpal bones and is quite rigid.
2. Distal Transverse Arch: runs transversely and is located at the MCP joints. MCP 1st, 4th, and 5th are mobile and MCP 2nd and 3rd are fixed and more stable. This allows for greater grasping force and manipulation of objects.
3. Longitudinal Arch: runs the length of the hands and is formed by the shape of the metatarsals and fingers.

Figure 1

Wrist Complex Joints

1. Radiocarpal Joint (Condyloid – biaxial)

Located between the distal radius and radioulnar disc and the proximal row of carpals (scaphoid, lunate, and triquetrum).

Closed-Pack Position: Fully extended and radially deviated

Open-pack Position: Neutral and ulnar deviated

2. Midcarpal Joint

Located between the proximal row of carpal bones and the distal row of carpal bones and has a joint capsule separate from the joint capsule of the radiocarpal joint.

3. Ulnocarpal Joint

The ulna itself does not directly articulate with the carpal bones  because of various soft tissue structures that exist there (i.e. articular disc), but does transmit approximately 20% of the load from the hand to the forearm when compression forces occur through the wrist.

Figure 2

Radiocarpal: Range of Motion

Flexion: 80° - Movement of the palm of hand toward the

anterior or volar aspect of the forearm.

Extension: 70° - Movement of the back of the hand toward the posterior or dorsal aspect of the forearm.

Radial Deviation: (abduction) 20° - Movement of the thumb side of hand toward the radial side of the forearm.

Ulnar Deviation: (adduction) 30° - Movement of the

little finger side of the hand toward the ulnar side of the

forearm.

                                                                        Hand and Finger Joints

Carpometacarpal (arthrodial - triaxial)

2nd – located between the trapezoid and base of the 2nd metacarpal.

3rd – located between the capitate and base of the 3rd metacarpal.

4th – located between the hamate and base of the 4th metacarpal.

5th – located between the hamate and base of the 5th 

metacarpal.

Note:

1. The 2nd and 3rd CMC joints are relatively rigid forming a stable center of the hand.
2. The 4th and 5th CMC joints are more mobile allowing the ulnar side of the hand to fold around the center of the hand. Some abduction and adduction also occurs at these joints.
3. Some slight medial and lateral rotation of the

5th CMC joint occurs to allow for opposition

and reposition of the little finger.

1st Carpometacarpal (thumb – sellar or saddle):

Flexion: 40° (frontal plane)

Extension: 10° (frontal plane)

Abduction: 60° (sagittal plane)

Adduction: 10° (sagittal plane)

Medial Rotation: 45°transverse plane)

Lateral Rotation: 0° (transverse plane)

Opposition: a combination of the movements of flexion, abduction, and medial rotation that allow the thumb to oppose the other fingers.

Reposition: movement of the thumb back to the anatomical position.

The deep fascia of the hand is continuous through the extensor and flexor retinacula with the antebrachial fascia. The central part of the palmar fascia – the palmar aponeurosis – is thick, tendinous, and triangular, and is continuous with the tendon of the Palmaris Longus (when present). The aponeurosis forms four distinct thickenings that radiate to the bases of the fingers and become continuous with the fibrous tendon sheaths of the digits. Many minute, strong skin ligaments (ligamentum retinacula cutis) extend from the palmar aponeurosis to the skin holding the skin close to the aponeurosis allowing only minimal sliding of the skin and thus promoting a firm grasp.

Figure 3

Wrist Joint Complex:  Misc. Structures

1. Radiocarpal Joint Capsule

The joint capsule is thickened and strengthened by the dorsal radiocarpal, palmar radiocarpal, radial collateral, and ulnar collateral ligaments.

2. Radioulnar Disc (Triangular Fibrocartilage)

This disc attaches to the distal end of the radius and ulna providing stability to the radiocarpal joint blending into the capsular and ligamentous structures of the wrist joint.

3. Transverse Carpal Ligament (Flexor Retinaculum)

Attaches medially to pisiform and hook of the hamate, and laterally to scaphoid and trapezium forming the palmar border (roof) of the carpal tunnel. As a retinaculum if helps keep the flexor tendons from bowstringing during wrist flexion.

4. Dorsal Carpal Ligament (Extensor Retinaculum)

Attaches medially to the styloid process of ulna, trapezium, and pisiform bones, and laterally to the radial styloid process. As a retinaculum if helps keep the extensor tendons from bowstringing during wrist extension.

figure 5              

Figure 6

Wrist Joint Complex:  Ligaments

1. Dorsal Radiocarpal Ligament

Located on the dorsal side of the wrist attaching from the dorsal surface of the distal radius to the carpal (scaphoid, lunate, triquetrum) bones. It functions to limit wrist flexion.

2. Palmar Radiocarpal Ligaments

Located on the palmar side of the wrist attaching from the palmar surface of the distal radius to the proximal row of carpal bones. It functions to limit wrist extension.

3. Radial Collateral Ligament

Attaches from the styloid process of the radius to the scaphoid and trapezium. It functions to limit ulnar deviation.

4. Ulnar Collateral Ligament

Attaches from the styloid process of the ulna to the pisiform and triquetrum. It functions to limit radial deviation.

Figure 7

e

Figure 8

Carpal Tunnel

Located on the palmar surface of the wrist, the borders of the carpal tunnel are formed by the:

1. Arch like concavity formed by the proximal and distal rows of carpal bones.
2. Transverse Carpal Ligament (also known as the flexor retinaculum) that spans across the top of the carpal bones attaching to the pisiform and hook of the hamate on the ulnar side, and the scaphoid and trapezium on the radial side.

The structures that pass through the carpal tunnel are:

1. Four tendons of the flexor digitorum superficialis
2. Four tendons of the flexor digitorum profundus
3. Tendon of the flexor pollicis longus
4. Median nerve

Note: all of the flexor tendons of the wrist and fingers pass through the carpal tunnel except for the Flexor Carpi Ulnaris, Flexor Carpi Radialis, and the Palmaris Longus.

figure 9

Carpal Tunnel Syndrome

A condition in which the median nerve that runs through the carpal tunnel is being compressed. This can be caused by inflammation, thickening of irritated tendons, or swelling that narrows the tunnel. This initially results in an alteration of sensation (tingling, numbness, and pain) to the palm side of the thumb, index and middle finger.

Worsening symptoms include muscle weakness, increased pain, decreased grip strength, and in chronic and/or untreated cases can cause muscle atrophy.

Figure 10

Guyon’s Canal Syndrome

A condition in which the ulnar nerve that runs through Guyon’s canal, located on the palmar side of the wrist and formed by two bones (pisiform and hamate) and the ligament that connects them, is being compressed. This initially results in a feeling of tingling in the little and ring fingers.

Symptoms may progress to a burning pain in the wrist and hand followed by decreased sensation in the little and ring fingers and even a gradual weakness in the intrinsic muscles of the hand making it hard to spread the fingers and pinch with the thumb.

Figure 11

The Dorsal Hood (Extensor Hood Mechanism)

Figure 12

Figure 13

Muscles that Cross the Wrist

Wrist Flexors (Palmar Wrist):

• Flexor Pollicis Longus
• Flexor Carpi Radialis
• Palmaris Longus
• Flexor Digitorum Superficialis
• Flexor Carpi Ulnaris
• Flexor Digitorum Profundus

Wrist Extensors (Dorsal Wrist):

• Extensor Carpi Ulnaris
• Extensor Digiti Minimi
• Extensor Digitorum
• Extensor Indicis
• Extensor Carpi Radialis Brevis
• Extensor Carpi Radialis Longus
• Extensor Pollicis Longus
• Extensor Pollicis Brevis
• Abductor Pollicis Longus

Flexor Pollicis Longus

Origin:

Insertion:

Actions:

Nerve Innervation:

Figure 14

Flexor Carpi Radialis

Origin:

Insertion:

Actions:

Nerve Innervation:

Palmaris Longus

Origin:

Insertion:

Actions:

Nerve Innervation:

Flexor Carpi Ulnaris

Origin:

Insertion:

Actions:

Nerve Innervation:

Muscles of the Wrist – “Palmar Side” Continued

Flexor Digitorum Superficialis

Origin:

Insertion:

Actions:

Nerve Innervation:

Figure 15

Flexor Digitorum Profundus

Origin:

Insertion:

Actions:

Nerve Innervation:

Muscles of the Wrist – “Dorsal Side”

Extensor Carpi Ulnaris

Origin:

Insertion:

Actions:

Nerve Innervation:

Figure 16

Extensor Digiti Minimi

Origin:

Insertion:

Actions:

Nerve Innervation:

Extensor Digitorum

Origin:

Insertion:

Actions:

Nerve Innervation:

Muscles of the Wrist – “Dorsal Side” Continued

Extensor Indicis

Origin:

Insertion:

Actions:

Nerve Innervation:

Figure 17

Extensor Carpi Radialis Brevis

Origin:

Insertion:

Actions:

Nerve Innervation:

Extensor Carpi Radialis Longus

Origin:

Insertion:

Actions:

Nerve Innervation:

Extensor Pollicis Longus

Origin:

Insertion:

Actions:

Nerve Innervation:

Extensor Pollicis Brevis

Origin:

Insertion:

Actions:

Nerve Innervation:

Abductor Pollicis Longus

Origin:

Insertion:

Actions:

Nerve Innervation:

Intrinsic Muscles of the Hand – “Thenar” Muscles

Opponens Pollicis

Origin:

Insertion:

Actions:

Nerve Innervation:

Figure 20

Abductor Pollicis Brevis

Origin:

Insertion:

Actions:

Nerve Innervation:

Flexor Pollicis Brevis

Origin:

Insertion:

Actions:

Nerve Innervation:

Intrinsic Muscles of the Hand – “Hypothenar” Muscles

Flexor Digiti Minimi

Origin:

Insertion:

Actions:

Nerve Innervation:

Figure 20

Opponens Digiti Minimi

Origin:

Insertion:

Actions:

Nerve Innervation:

Abductor Digiti Minimi

Origin:

Insertion:

Actions:

Nerve Innervation:

Intrinsic Muscles of the Hand – “Intermediate” Muscles

Adductor Pollicis

Origin:

Insertion:

Actions:

Nerve Innervation:

Figure 21

Figure 22

Palmar Interossei

Origin:

Insertion:

Actions:

Nerve Innervation:

Dorsal Interossei

Origin:

Insertion:

Actions:

Nerve Innervation:

Lumbricals

Origin:

Insertion:

Actions:

Nerve Innervation:

Damage to the Median Nerve

Median Nerve Damage (Hand of Benediction)

Results from prolonged compression or injury to the Median nerve at the level of the elbow or upper arm. Results in an inability to flex the index and middle fingers. This is due to a loss of innervation to the 1 & 2 Lumbricles of the hand and the radial half of the Flexor Digitorum Profundus – supplied by the Median nerve. However, the Extensor Digitorum is left unopposed and continues to pull causing hyperextension at the MCP joints of these fingers. Typically only manifests when the person is asked to make a fist.

Figure 23

Damage to the Ulnar Nerve

Ulnar Nerve Damage (Ulnar Claw Hand)

A hand in ulnar claw position will have the 4th and 5th MCP joints hyperextended and the interphalangeal joints flexed towards the palm.

Figure 24

Damage to the Radial Nerve

 Radial Nerve Damage (Wrist Drop)

Lack of innervation to the wrist extensors (The “E” in BEAST) would cause the wrist to drop when gravity acts upon it. The wrist flexors would be pulling against the denervated wrist extensors causing wrist flexion to occur. At the same time, the supinator muscle would also lack innervation and therefore the forearm would be pulled into a pronated position.

Figure 25

A Few Wrist and Hand Review Questions