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Extensor carpi radialis longus tendon

The extensor carpi radialis longus (ECRL) tendon is the distal tendinous continuation of the ECRL muscle, one of the major wrist extensors in the posterior compartment of the forearm. It lies superficial and lateral, contributing to wrist extension and radial deviation. The tendon is long, cord-like, and passes beneath the extensor retinaculum within the second dorsal compartment along with the tendon of the extensor carpi radialis brevis (ECRB).

The ECRL tendon plays an essential role in dynamic wrist stability, particularly during gripping and lifting. It is often harvested as a tendon graft for reconstructive surgery due to its length and consistent anatomy.

Synonyms

  • Tendon of extensor carpi radialis longus

  • Radial wrist extensor tendon

  • ECRL distal tendon

Origin, Course, and Insertion

  • Origin (muscular): Lateral supracondylar ridge of the humerus and adjacent lateral intermuscular septum.

  • Course (tendinous): The tendon forms in the distal third of the forearm, running superficially along the lateral border of the radius. It passes deep to the brachioradialis tendon and beneath the extensor retinaculum within the second dorsal compartment.

  • Insertion: Dorsal surface of the base of the second metacarpal bone, radial side.

Tendon Attachments

  • Proximal: Continuation of the ECRL muscle belly.

  • Distal: Inserts on the base of the second metacarpal, occasionally giving a slip to the base of the third metacarpal.

  • Retinacular relationship: Enclosed in a synovial sheath beneath the extensor retinaculum, sharing a compartment with the ECRB tendon.

Relations

  • Anteriorly: Radius and brachioradialis tendon.

  • Posteriorly: Superficial fascia of the forearm and skin.

  • Medially: Extensor carpi radialis brevis tendon.

  • Laterally: Brachioradialis muscle and tendon.

  • At wrist: Crosses dorsally under the extensor retinaculum lateral to the Lister’s tubercle.

Nerve Supply

  • Radial nerve (C6–C7), specifically via its muscular branch before entering the forearm.

Function

  • Primary: Extends and abducts (radially deviates) the wrist joint.

  • Secondary: Assists in stabilizing the wrist during finger flexion and gripping.

  • Dynamic stabilizer: Provides lateral wrist stability during heavy load bearing.

  • Clinical role: A key structure in wrist overuse syndromes, lateral epicondylitis, and tendon transfer procedures.

Clinical Significance

  • Tendinopathy: Overuse causes pain along the lateral forearm or dorsal wrist; seen in racquet sports and repetitive lifting.

  • Tendon tear or rupture: May follow trauma or degenerative changes; leads to weak wrist extension and grip instability.

  • Intersection syndrome: ECRL tendon may be involved where it crosses the first dorsal compartment tendons.

  • Tenosynovitis: Inflammation of its synovial sheath beneath the retinaculum causes pain and swelling over the dorsal wrist.

  • Surgical relevance: Commonly used in tendon transfers for radial nerve palsy or thumb extension reconstruction.

MRI Appearance

  • T1-weighted images:

    • Normal tendon: Low signal (dark) linear band with smooth margins.

    • Peritendinous fat: Bright, clearly separating tendon from surrounding tissue.

    • Muscle belly: Intermediate signal intensity.

    • Pathology: Tendon thickening or partial tear appears as focal intermediate-to-bright signal with contour irregularity.

  • T2-weighted images:

    • Normal tendon: Low signal (dark) due to tightly packed collagen fibers.

    • Pathologic tendon: Bright hyperintense areas within tendon substance or sheath indicate tendinosis or tear.

    • Muscle: Intermediate signal, slightly darker than on T1.

    • Peritendinous edema: Hyperintense signal surrounding the tendon sheath.

  • STIR:

    • Normal tendon: Dark linear structure with uniform signal.

    • Pathology: Bright hyperintense regions correspond to edema, inflammation, or microtears.

    • Useful for detecting early tenosynovitis or peritendinous fluid.

  • Proton Density Fat-Saturated (PD FS):

    • Normal tendon: Dark, sharply defined structure.

    • Partial tear or tendinitis: Focal bright signal within tendon substance or at its insertion on the base of the second metacarpal.

    • Chronic tendinopathy: Mild irregularity with heterogeneous low-to-intermediate signal.

  • T1 Fat-Sat Post-Contrast:

    • Normal tendon: Minimal or no enhancement.

    • Inflamed tendon sheath: Linear or rim enhancement along synovial sheath.

    • Tendinosis or partial tear: Peripheral or patchy enhancement due to vascular granulation tissue.

    • Complete tear: Enhancement around a gap filled with fluid or granulation tissue.

CT Appearance

Non-Contrast CT:

  • Tendon: Seen as a fine soft-tissue band crossing the dorsal radius and wrist.

  • Bony insertion: May show tiny cortical irregularities in chronic tendinopathy.

  • Calcific tendinitis: Appears as small hyperdense foci within or near the tendon insertion.

  • Adjacent fat planes: Preserve tendon outline; distortion indicates inflammation or scarring.

Post-Contrast CT (standard):

  • Tendon enhancement: Minimal in normal cases.

  • Inflamed tendon sheath: Shows subtle enhancement along the course of the tendon.

  • Tendon tears: Visible as localized discontinuity or irregularity with adjacent soft-tissue enhancement.

  • Postoperative or chronic cases: May reveal scarring or ossification near insertion.

MRI image

Extensor carpi radialis longus tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Extensor carpi radialis longus tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI image

Extensor carpi radialis longus tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

CT image

Extensor carpi radialis longus tendon CT AXIAL IMAGE

CT image

Extensor carpi radialis longus tendon CT