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Lateral supracondylar ridge

The lateral supracondylar ridge is a prominent bony ridge located on the distal third of the humerus, extending from the deltoid tuberosity down to the lateral epicondyle. It serves as a key osseous landmark and attachment site for several muscles of the forearm and arm. Structurally, it forms the lateral border of the distal humerus and provides strength and stability to the distal shaft during upper limb motion.

The ridge gives rise to the brachioradialis and extensor carpi radialis longus muscles, and its lower portion contributes to the attachment of the lateral intermuscular septum, which separates the anterior (flexor) and posterior (extensor) compartments of the arm.

Synonyms

  • Lateral supracondyloid ridge

  • Lateral border of the distal humerus

  • External supracondylar line

Location and Structure

  • The lateral supracondylar ridge is a bony elevation on the distal humeral shaft.

  • It extends obliquely downward and anteriorly from the deltoid tuberosity to the lateral epicondyle.

  • It is composed of dense cortical bone, providing robust anchorage for muscles and fascia.

  • The ridge forms the lateral boundary of the distal humerus, opposite the medial supracondylar ridge.

Relations

  • Anteriorly: Brachioradialis and extensor carpi radialis longus muscles

  • Posteriorly: Triceps brachii (lateral head)

  • Medially: Shaft of the humerus and lateral intermuscular septum

  • Laterally: Deep fascia of the arm and overlying skin

  • Inferiorly: Lateral epicondyle of the humerus

Attachments

  • Upper part: Origin of the brachioradialis muscle

  • Middle part: Origin of the extensor carpi radialis longus muscle

  • Lower part: Attachment of the lateral intermuscular septum, separating flexor and extensor compartments of the arm

Function

  • Provides strong osseous support for the distal humeral shaft

  • Serves as muscular origin for key forearm extensors

  • Acts as an anatomical landmark for surgical orientation and imaging

  • Contributes to mechanical leverage and stability at the elbow joint during extension and supination movements

Clinical Significance

  • Fractures: Commonly involved in supracondylar and distal humeral fractures, especially in trauma or falls on an outstretched hand

  • Muscle strain or avulsion: Overuse or sudden contraction of the brachioradialis or extensor carpi radialis longus may cause avulsion at the ridge

  • Surgical landmark: Important during posterior approach to the humerus and fixation of distal humeral fractures

  • Osteophyte formation: Chronic stress or enthesopathy can lead to periosteal thickening or bony spurs

  • Imaging relevance: Key for identifying muscle origins, fracture lines, or cortical disruptions on radiographs and advanced imaging

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark line) with smooth contour

    • Bone marrow: Bright fatty signal within the distal humeral shaft

    • Muscle attachments: Seen as low-signal tendinous insertions adjacent to ridge

    • Pathology: Fracture lines appear as linear low-signal defects through cortex or subcortical region

  • T2-weighted images:

    • Cortex: Low signal intensity

    • Marrow: Bright, slightly less intense than T1

    • Soft tissues: Clear differentiation of muscle and septal attachments

    • Pathology: Edema or periosteal reaction appears hyperintense near ridge; cortical irregularities highlight avulsion or stress injury

  • STIR:

    • Normal bone: Intermediate-to-dark signal

    • Pathologic changes: Bright hyperintense areas in marrow or periosteum indicating edema, contusion, or enthesitis

    • Excellent for detecting stress injuries and early periostitis

  • Proton Density Fat-Saturated (PD FS):

    • Normal marrow: Intermediate-to-dark signal

    • Pathology: Focal bright signal near muscle attachments or cortical margin indicating microtrauma, partial avulsion, or inflammation

    • Helpful for evaluating tendinous attachment pathology

  • T1 Fat-Sat Post-Contrast:

    • Normal bone: Mild uniform enhancement of marrow

    • Active inflammation or fracture: Focal enhancement of periosteum or surrounding soft tissues

    • Chronic enthesopathy: Minimal peripheral enhancement with low-signal fibrosis

CT Appearance

Non-Contrast CT:

  • Cortex: High attenuation, sharply defined ridge along distal lateral humerus

  • Marrow cavity: Intermediate attenuation with visible trabecular pattern

  • Muscular attachments: Appear as thin soft-tissue densities merging with bone surface

  • Pathology: Detects cortical breaks, periosteal thickening, or avulsion fragments with high spatial resolution

Post-Contrast CT (standard):

  • Bone: Enhances minimally and uniformly

  • Soft tissues: Enhanced visualization of inflamed or thickened periosteum and adjacent muscle origins

  • Useful in complex fractures, postoperative assessment, and chronic enthesopathic changes

CT VRT 3D image

Lateral supracondylar ridge 3D VRT IMAGE

MRI image

Lateral supracondylar ridge coronal cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000

MRI image

Lateral supracondylar ridge coronal cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000

CT image

Lateral supracondylar ridge ct coronal image