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Forearm (Radio-ulnar Joints) and Wrist Joint

OVERVIEW

 

Forearm:

  • Rotation of the forearm allows for precise positioning of the hand in space.
  • Forearm rotation also allows for various power activities of the hand such as turning a key.
  • The muscles acting here can be denervated in various patterns of peripheral nerve injury such as that of the median nerve.
  • Restoration, especially of pronation is critical for normal upper extremity function.

Wrist:

  • Motion at the wrist joint serves to precisely position the hand for functional activity.
  • Wrist extension allows for better power grip of the hand.
  • The muscles acting here can be denervated in peripheral nerve injury.
  • Restoration of wrist motion is secondary to that of shoulder, elbow and hand function.

 

FOREARM

Structures of the Forearm

  • Bones:
    • Radius
    • Ulna

  • The forearm joints are composed of the proximal and distal radio-ulnar joints.

Movements of the Forearm

  • Rotation of the radius around the ulnar allows for forearm supination and pronation.

Muscles of the Forearm Radio-ulnar Joint

Muscle Name

Innervation

Action

Pronator teres

Median nerve

Forearm pronation.

Pronator quadratus

Median nerve

Forearm pronation.

Biceps Brachii

Musculocutaneous nerve

Forearm supination (primary supinator of the forearm)

Supinator

Radial nerve

Forearm supination.

 

WRIST

Structures of the Wrist

  • Bones
    • Radius
    • Ulna
    • Carpal bones

  • Joints (for the purposes of discussing peripheral nerve injury, the complex anatomy of the wrist joint is not as critical to delve into):

    • Radiocarpal joint
    • Mid-carpal joint

    • Distal radioulnar joint

Movements of the Wrist

  • Flexion and extension are movements about a coronal axis.

  • Abduction (radial deviation) and adduction (ulnar deviation) are movements about a sagittal axis.
  • Circumduction includes a combination of flexion, abduction, extension, and adduction of the radio-carpal and midcarpal joints.

Muscles of the Wrist Joint

Muscle Name

Innervation

Action

Palmaris longus

Median nerve

Assists in flexion of wrist.

Flexor carpi radialis

Median nerve

Flexes and radially deviates wrist.

Flexor carpi ulnaris

Median nerve

Flexes and ulnarly deviates wrist.

Extensor carpi radialis longus

Radial nerve

Extends and radially deviates wrist.

Extensor carpi radialis brevis

Radial nerve

Extends and radially deviates wrist.

Extensor carpi ulnaris

Radial nerve

Extends and ulnarly deviates wrist.

Italics -- Note that there are additional muscles that assist or may assist but are not the primary action of wrist flexion and extension, abduction and adduction, and circumduction