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Flexor Carpi Radialis (FCR)

OVERVIEW
Key Points:
• Flexes and abducts the wrist.
• Tendon transfers – The flexor carpi radialis (FCR) is the better wrist flexor to use compared to the flexor carpi ulnaris (FCU) in radial nerve palsy patients. FCU is stronger wrist flexor than FCR and the power wrist flexor for manual labor.

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EXAMINATION
Muscle Function:
Primary: Flexes and abducts the wrist.
Secondary: May assist in pronation of the forearm and in flexion of the elbow.
Palpation: The tendon is lateral to the palmaris longus tendon and most superficial in line with the second metacarpal. It is a broader tendon than the palmaris longus and runs at a slight diagonal originating from the medial epicondyle towards the wrist.
 
Strength Testing:
Gravity-lessened Test: Position – the subject in sitting with elbow slightly flexed and forearm in supination. The forearm is rested on a table, wrist at the edge, and hand off the edge. Fingers are in a relaxed position. Stabilize – the forearm with the hand supported. Support - through the range of motion.
 
Anti-gravity Test: Position – the subject in sitting with elbow slightly flexed and forearm in neutral position. The forearm is rested on a table, wrist at the edge, and hand off the edge. Fingers are in relaxed position. Stabilize – the forearm with the hand supported. Resist – against flexion and radial deviation of the wrist (in the direction of wrist extension and ulnar deviation).
 
Possible Substitutions: Muscles for finger flexion. To avoid this, keep fingers relaxed and palpate the flexor carpi radialis tendon.  A second potential substitution would be the palmaris longus.  To differentiate this, palpate the correct muscle is being tested.
 
Relevant Anatomy:
Innervation:
• Roots: C6, C7.
• Nerve: Median nerve.
• Innervation Route: C6, C7 → median nerve → flexor carpi radialis branch.
Origin: Common flexor tendon from medial epicondyle of humerus and deep antebrachial fascia.
 
Insertion: Base of second metacarpal bone and slip to base of third metacarpal bone.