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 inferoposteriorly 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. Occasionally, there may be an attachment to the lateral epicondyle by the common extensor tendon.[1]
Insertion
- Posterior surface of the base of the second metacarpal.[1]
Innervation
- Radial nerve (root value C6 and C7) from the posterior cord of the brachial plexus.[1]
Blood supply
Function
Extensor carpi radialis longus together with extensor carpi radialis brevis produce wrist extension and abduction (radial deviation). In addition extensor carpi radialis longus may help to flex the elbow joint and is active during fist clenching.[1]
Clinical relevance
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. Functionally, the wrist extensors work strongly in the action of gripping, together with extensor carpi ulnaris. By maintaining the wrist in an extended position, flexion of the wrist under the action of flexors digitorum superficialis and profundus is prevented, with the result that these muscles act on the fingers. If the wrist is then allowed to flex the flexor tendons cannot shorten sufficiently to produce effective movement at the interphalangeal joints. This therefore becomes a state of active insufficiency.
Radial nerve damage leads to paralysis of the wrist extensors. This leads to a decreased grip strength. However, with the wrist splinted in extension, the tendons of flexors digitorum superficialis and profundus act on the fingers and a functional grip can be obtained.[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 both extensors carpi radialis longus and brevis can be palpated in the upper lateral aspect of the posterior part of the forearm. The tendons, particularly longus, can be palpated in the floor of the anatomical snuff box if the same movement of extension and abduction is carried out.[1]
Treatment
- Control of pain[2]
- Soft tissue therapy[2]
- Manual therapy – elbow and wrist[2]
- Stretching[2]
- Muscle strengthening[2]
See also
Resources
