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Anterior root of lateral meniscus

The anterior root of the lateral meniscus is the attachment site of the anterior horn of the lateral meniscus to the tibial plateau. It anchors the lateral meniscus firmly in the anterior intercondylar region, just posterior to the insertion of the anterior cruciate ligament (ACL). This root is critical for maintaining meniscal stability, load transmission, and protecting the articular cartilage.

Although less frequently injured than the posterior root of the medial meniscus, the anterior root of the lateral meniscus can be torn in acute trauma, ACL injuries, or degenerative processes. Root avulsions or tears compromise meniscal hoop stress, leading to extrusion and rapid progression of lateral compartment osteoarthritis.

Synonyms

  • Anterior horn root of the lateral meniscus

  • Tibial root of the anterior lateral meniscus

  • Anterior lateral meniscal attachment

Relations

  • Superiorly: Lateral femoral condyle articular cartilage

  • Inferiorly: Tibial plateau, anterior intercondylar region

  • Anteriorly: Tibial attachment of the anterior cruciate ligament (ACL)

  • Posteriorly: Body of the lateral meniscus

  • Laterally: Joint capsule and anterior meniscotibial attachments

  • Medially: Intercondylar notch structures

Function

  • Anchoring: Provides firm tibial fixation for the anterior horn of the lateral meniscus

  • Load transmission: Allows effective conversion of compressive forces into hoop stresses

  • Joint stability: Works synergistically with the ACL to resist anterior tibial translation

  • Shock absorption: Protects tibial plateau cartilage during high axial loads

  • Kinematics: Facilitates normal meniscal movement during flexion and extension

Clinical Significance

  • Root tears: Less common than posterior root tears but clinically significant

  • Association: Often occur with ACL injuries or traumatic twisting events

  • Consequence: Root avulsion leads to meniscal extrusion, altered biomechanics, and rapid cartilage degeneration

  • Symptoms: Joint pain, instability, swelling, mechanical clicking, or giving way

  • Surgical importance: Repair is crucial; untreated tears accelerate lateral compartment osteoarthritis

  • Imaging role: MRI is gold standard; CT arthrography is useful when MRI is contraindicated

MRI Appearance

  • T1-weighted images:

    • Normal root: low signal (dark), triangular attachment

    • Tear or avulsion: intermediate signal gap at tibial attachment

    • Adjacent bone marrow edema may appear as intermediate signal changes

  • T2-weighted images:

    • Normal root: uniformly dark

    • Tears: bright linear or irregular signals disrupting root attachment

    • Root avulsions: high signal gap at insertion, sometimes with associated ACL tear

  • STIR:

    • Normal root: dark signal

    • Pathology: hyperintense signal indicating edema, fluid, or partial avulsion

  • Proton Density Fat-Saturated (PD FS):

    • Normal: compact, dark low-signal root

    • Tear: bright signal clefts or defects extending into tibial surface

    • Excellent for subtle partial-thickness tears and root detachments

  • T1 Fat-Sat Post-Contrast:

    • Normal root: minimal or no enhancement

    • Post-surgical repair: enhancing scar tissue

    • Persistent non-enhancing defects = recurrent or persistent tear

MRI Arthrogram Appearance

  • Contrast outlines the root attachment and tracks into root tear clefts

  • Confirms communication with the articular surface in avulsions

  • Helpful in distinguishing degeneration (no contrast entry) from true tear (contrast entry)

  • Valuable in evaluating ACL-associated root injuries

CT Appearance

Non-Contrast CT:

  • Root not well visualized (small soft tissue density at tibial plateau)

  • Indirect signs: joint space narrowing, subchondral sclerosis, marginal osteophytes

Post-Contrast CT (standard):

  • Root remains poorly defined without intra-articular contrast

  • Only perimeniscal changes may be inferred

CT Arthrogram Appearance

  • Contrast sharply defines the anterior root attachment

  • Linear contrast-filled clefts indicate root tears

  • Contrast pooling at tibial insertion suggests avulsion

  • Superior to routine CT for evaluating meniscal root pathology, especially in patients unable to undergo MRI

MRI images

Anterior root of lateral meniscus axial cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI images

Anterior root of lateral meniscus coronal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI images

Anterior root of lateral meniscus sagittal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000