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Meniscus cartilage

The menisci are crescent-shaped fibrocartilaginous structures within the knee joint. Each knee has two menisci: the medial meniscus and the lateral meniscus. They act as shock absorbers, stabilizers, and load distributors between the femur and tibia. The menisci deepen the tibial articular surface, protect articular cartilage, and facilitate smooth knee movements.

The medial meniscus is more C-shaped, broader posteriorly, and firmly attached to the joint capsule and medial collateral ligament, making it more prone to injury. The lateral meniscus is circular (O-shaped), smaller, more mobile, and less frequently injured.

Synonyms

  • Knee fibrocartilage

  • Medial and lateral semilunar cartilages

  • Meniscal cartilage

Origin,Course, and Insertions

  • Origin (embryologic): Derived from interzone mesenchymal tissue during embryonic joint development

  • Course (shape and extent):

    • Medial meniscus: C-shaped, runs along medial tibial plateau

    • Lateral meniscus: O-shaped, runs along lateral tibial plateau, nearly complete circle

  • Branches (segments): Each meniscus has an anterior horn, body, and posterior horn

  • Insertions (attachments):

    • Medial meniscus: Anterior horn to anterior intercondylar area (anterior to ACL), posterior horn to posterior intercondylar area (anterior to PCL)

    • Lateral meniscus: Anterior horn to anterior intercondylar area (posterior to ACL), posterior horn to posterior intercondylar area (anterior to posterior meniscofemoral ligament)

Relations

  • Superiorly: Femoral condyles (articular cartilage)

  • Inferiorly: Tibial plateau

  • Medially: Medial collateral ligament (for medial meniscus)

  • Laterally: Popliteus tendon (related to lateral meniscus)

  • Anteriorly: Patellar ligament via fat pad

  • Posteriorly: Posterior capsule, cruciate ligaments (ACL and PCL)

Function

  • Distribute weight-bearing forces across knee joint

  • Shock absorption during movement and impact

  • Increase joint congruency between femoral condyles and tibial plateau

  • Assist in lubrication and nutrition of articular cartilage

  • Provide proprioceptive input to stabilize knee mechanics

Clinical Significance

  • Meniscal tears are common sports and degenerative injuries (bucket-handle, radial, horizontal, flap)

  • Medial meniscus is more commonly injured due to reduced mobility

  • Lateral meniscus injuries often occur with ligamentous injuries (ACL tears)

  • Meniscus degeneration seen in osteoarthritis

  • MRI is gold standard for meniscus evaluation

  • Meniscectomy or meniscus repair may be required surgically

MRI Appearance

T1-weighted images:

  • Meniscus appears as a dark (low-signal) wedge-shaped structure between femoral condyle and tibial plateau

  • Tears may appear as linear or complex high-signal lines extending to the articular surface

T2-weighted images:

  • Meniscus remains dark (low signal) due to fibrocartilage composition

  • Tears show bright (hyperintense) linear or complex signals extending to articular surface

STIR (Short Tau Inversion Recovery):

  • Normal meniscus: dark (low signal)

  • Tears: bright hyperintensity within the meniscus, especially if fluid-filled

Proton Density Fat-Saturated (PD FS):

  • Normal meniscus: dark wedge-shaped structure

  • Tears: appear as bright signal extending to surface; gold standard sequence for meniscal injury

T1 Fat-Sat Post-Contrast:

  • Normal meniscus does not enhance significantly

  • Postoperative or inflamed meniscus may show peripheral or irregular enhancement

  • Enhancing scar tissue can be differentiated from non-enhancing recurrent tear

MRI Arthrogram Appearance

  • Intra-articular gadolinium outlines the meniscus

  • Tears are seen when contrast penetrates into or through the meniscus

  • More sensitive for subtle or postoperative tears compared to standard MRI

CT Appearance

Non-Contrast CT:

  • Menisci are not well visualized directly (soft tissue density similar to cartilage)

  • Secondary signs such as joint space narrowing, osteophytes, or displaced fragments may be seen

Post-Contrast CT:

  • Contrast does not enhance normal meniscus

  • Inflammatory or postsurgical changes may enhance adjacent soft tissues

CT Arthrogram Appearance

  • Iodinated contrast fills the joint space, outlining the meniscus

  • Meniscal tears appear as linear contrast extension into meniscal substance or through to the articular surface

  • Useful in patients who cannot undergo MRI

MRI image

meniscus cartilage coronal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

MRI image

meniscus cartilage axial cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

CT image

meniscus cartilage ct image