Forearm and Wrist

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