Extensor Carpi Radialis Longus
Original Editor - Wanda van Niekerk
Top Contributors - Wanda van Niekerk, Nina Myburg, Kim Jackson, Carina Therese Magtibay, Rachael Lowe, Amanda Ager and Aya Alhindi
Description
Extensor carpi radialis longus is a muscle that can be found in the posterior compartment of the forearm. It is partly overlapped by brachioradialis and these muscles often blend together. As its name suggests it is a wrist extensor and can be palpated infero-posteriorly to the elbow.
Structure
Extensor carpi radialis longus is a fusiform muscle that forms a flattened tendon which runs distally over the lateral surface of the radius. In the lower third of the forearm the tendon, together with that of extensor carpi radialis brevis, is crossed by the tendons of abductor pollicis brevis and extensor pollicis brevis. The tendons of extensor carpi radialis longus and brevis pass deep to the extensor retinaculum in a common synovial sheath. Together they groove the posterior surface of the styloid process of the radius.[1]
Origin
- Anterior lower third of the lateral supracondylar ridge of the humerus and adjacent intermuscular septum. Sometimes, it may be attached to the lateral eipcondyle by the common extensor tendon.[1]
Insertion
- The radial side of the dorsal surface of the base of the second metacarpal bone.
Innervation
- Radial nerve (root value C6 and C7) from the posterior cord of the brachial plexus.[1]The roots of C5 and C6 innervate the skin over the muscle.[1]
Blood supply
- Radial artery[1]
Function
- Extensor carpi radialis longus together with extensor carpi radialis brevis produce wrist extension and abduction (radial deviation).
- It also may help to flex the elbow joint and is active during fist clenching.[1]
- Extensor carpi radialis longus is one of three primary wrist extensors. It is most effective as a wrist extensor when the elbow is extended and when radial deviation is balanced by the primary ulnar deviator- extensor carpi ulnaris.
Clinical Relevance
Functionally, the wrist extensors work strongly in the action of gripping, together with extensor carpi ulnaris. By keeping the wrist in extension, flexion of the wrist by flexors digitorum superficialis and profundus is prevented, with the result that these muscles act on the fingers. When the wrist then moves into flexion, the flexor tendons are unable to shorten enough to generate effective movement at the interphalangeal joints, resulting in a state of active insufficiency.[1]
Radial nerve damage leads to paralysis of the wrist extensors. This leads to a decreased grip strength. However, when the wrist is stabilised (splinted) in extension, the flexor digitorum superficialis and profundus tendons effectively engage the fingers and this allows for a functional grip.[1]
Intersection Syndrome is a bursitis that occurs at the site where the abductor pollicis longus and extensor pollicis brevis tendons cross over the extensor carpi radialis tendons proximal to the extensor retinaculum. This may be due to friction at this site of crossing or it may occur from tenosynovitis of the two extensor tendons within their synovial sheath. This leads to tenderness, swelling and crepitus and can be confused with de Quervain's syndrome. This condition is often seen in rowers, but also in canoeists and racket sportsmen.[2]
Assessment
Active movements
- Elbow flexion/extension
- Supination/pronation
- Wrist flexion/extension
- Radial/ulnar deviation
Passive movements
- Elbow flexion/extension
- Supination/pronation
- Wrist flexion/pronation
- Radial/ulnar deviation
Resisted movements
- Wrist extension
- Wrist abduction (radial deviation)
- Wrist extension together with abduction
- Grip test
Palpation
- Lateral epicondyle[2]
- With resisted wrist extension and abduction, the extensor carpi radialis longus and brevis can be palpated in the upper lateral portion of the posterior forearm. The tendon of extensor carpi radialis longus, in particular, can be felt in the floor of the anatomical snuffbox when these movements (wrist extension and abduction) are performed.[1]
See Also
Resources
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Soames R. Anatomy and human movement: structure and function. Eight Edition. Elsevier Limited. 2025.
- ↑ 2.0 2.1 Brukner P. Khan K. Clinical sports medicine. McGraw-Hill: 2006.
- ↑ Dr. Borst's Occupational Therapy Classroom. MMT Individual Muscle Extensor Carpi Radialis Longus (ECRL). Available from: https://www.youtube.com/watch?v=rR2dSbH12ig [last accessed 14/02/2025]
- ↑ RandaRamnarine. palpating extensor carpi radialis longus. Available from: https://www.youtube.com/watch?v=Xdinnbur_6w [last accessed 14/02/2025]