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Lateral epicondyle of humerus

The lateral epicondyle of the humerus is a prominent bony projection on the lateral distal end of the humerus, just above the capitulum. It serves as a key attachment site for the common extensor tendon and several forearm muscles that extend the wrist and fingers. This bony landmark is easily palpable on the outer aspect of the elbow and forms part of the lateral contour of the joint.

It acts as a mechanical anchor for the extensor muscles of the forearm and the lateral collateral ligament complex, providing stability to the radiohumeral and humeroulnar joints. Because of its exposed position and load-bearing role in repetitive wrist extension, it is a common site of tendinopathy and enthesopathy, clinically known as lateral epicondylitis (tennis elbow).

Synonyms

  • External condyle of humerus

  • Lateral humeral epicondyle

  • Common extensor origin

Location and Structure

  • Situated on the lateral aspect of the distal humerus, superior and posterior to the capitulum.

  • Projects laterally and slightly posteriorly, forming a rough, elevated surface.

  • Covered by tendinous attachments and joint capsule fibers.

  • The articular surfaces of the capitulum lie immediately inferior to it, forming the articulation with the radial head.

  • The epicondyle’s cortical bone is thick and dense to withstand mechanical stress from tendon traction.

Attachments

  • Muscular attachments (Common Extensor Origin):

    • Extensor carpi radialis brevis

    • Extensor digitorum

    • Extensor digiti minimi

    • Extensor carpi ulnaris

    • Supinator (partly)

    • Anconeus (adjacent)

  • Ligamentous attachments:

    • Lateral (radial) collateral ligament of the elbow joint

    • Annular ligament fibers blend near its inferior aspect

  • Capsular attachment:

    • Contributes to the lateral portion of the elbow joint capsule

Relations

  • Anteriorly: Capitulum and radiohumeral joint capsule

  • Posteriorly: Anconeus muscle and posterior aspect of elbow capsule

  • Superiorly: Lateral supracondylar ridge

  • Inferiorly: Lateral collateral ligament complex and radial head articulation

  • Laterally: Common extensor tendon and subcutaneous tissue

  • Medially: Olecranon fossa and trochlea separated by bony ridge

Function

  • Provides attachment and leverage for wrist and finger extensor muscles

  • Acts as an anchor point for the lateral ligament complex, maintaining elbow stability

  • Serves as a palpation landmark for clinical assessment of lateral elbow pain

  • Facilitates transmission of mechanical forces from the forearm extensors to the humerus

Clinical Significance

  • Lateral epicondylitis (tennis elbow): Degenerative tendinopathy of the common extensor origin due to overuse; pain localized at lateral epicondyle and radiating down forearm

  • Avulsion injuries: Seen in athletes or trauma involving sudden contraction of extensors

  • Fractures: May accompany distal humeral fractures or elbow dislocations

  • Osteochondral lesions: Chronic traction may cause cortical irregularities or spurring

  • Post-surgical relevance: Landmark for lateral approaches in elbow surgeries and reconstruction of ligamentous structures

  • Imaging importance: Key reference point in MRI and CT for diagnosing tendinopathy, tears, enthesopathy, and cortical integrity

MRI Appearance

  • T1-weighted images:

    • Cortical bone: low signal (dark)

    • Bone marrow: bright due to fatty content in adults

    • Common extensor tendon: low signal, blending with cortical bone at attachment

    • Pathology: intermediate to bright signal at tendon insertion in tendinosis or tear

    • Adjacent fat planes and soft tissues: bright, providing good contrast

  • T2-weighted images:

    • Normal cortex: dark

    • Marrow: bright, less intense than on T1

    • Common extensor origin: normally dark; tendinopathy or partial tear shows hyperintense signal at attachment

    • Bone marrow edema or inflammation: bright hyperintense region beneath cortex

  • STIR:

    • Normal bone: intermediate-to-dark

    • Pathologic tendon insertion or marrow edema: bright hyperintense signal

    • Detects early tendinosis and peritendinous inflammation with high sensitivity

  • Proton Density Fat-Saturated (PD FS):

    • Normal cortex and tendon: low signal

    • Partial tear or tendinosis: focal bright hyperintensity within or around tendon insertion

    • Excellent for evaluating subtle extensor tendon pathology and enthesopathy

  • T1 Fat-Sat Post-Contrast:

    • Normal epicondyle: minimal enhancement

    • Tendinopathy or lateral epicondylitis: focal or diffuse enhancement at tendon attachment

    • Bone marrow inflammation or cortical defect: enhancing signal surrounding epicondyle

CT Appearance

Non-Contrast CT:

  • Cortex: high-density, sharply defined outline

  • Trabecular bone: fine honeycomb pattern

  • Common extensor origin: seen as soft-tissue density attached to lateral cortical margin

  • Chronic enthesopathy: irregular cortical surface or small osteophyte formation

  • Fractures: linear lucent lines or cortical discontinuities around epicondyle

Post-Contrast CT (standard):

  • Enhancing soft-tissue changes may indicate inflammation or postoperative scarring

  • Helpful in distinguishing enthesopathy, ossification, or chronic inflammatory changes

CT VRT 3D image

Lateral epicondyle of humerus 3D VRT image

CT VRT 3D image

Lateral epicondyle of humerus 3d vrt

MRI image

Lateral epicondyle of humerus axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000

MRI image

Lateral epicondyle of humerus coronal cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000