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Medial meniscus

The medial meniscus is a crescent-shaped fibrocartilaginous structure located within the knee joint. It is interposed between the femoral condyle and the tibial plateau, acting as a cushion and stabilizer for load transmission across the joint. Compared to the lateral meniscus, it is broader, more firmly attached, and less mobile, which predisposes it to injury. It is clinically significant due to its role in meniscal tears, knee osteoarthritis, and as a landmark in knee arthroscopy and imaging.

Synonyms

  • Internal meniscus

  • Medial semilunar cartilage

  • Tibial meniscus (medial portion)

Origin, Course, and Insertions

  • Anterior horn: Attached to the anterior intercondylar area of the tibia, anterior to the anterior cruciate ligament (ACL) attachment

  • Course: Extends posteriorly along the medial tibial plateau, forming a broad C-shaped structure with a wider posterior segment

  • Posterior horn: Attached to the posterior intercondylar area of the tibia, between the attachments of the posterior cruciate ligament (PCL) and lateral meniscus

  • Peripheral attachments: Firmly anchored to the tibial plateau via the coronary ligaments and to the joint capsule

  • Connections: Connected to the deep fibers of the medial collateral ligament (MCL), further limiting its mobility

Relations

  • Superiorly: Medial femoral condyle (articulating surface)

  • Inferiorly: Medial tibial plateau

  • Anteriorly: Anterior cruciate ligament (close to anterior horn)

  • Posteriorly: Posterior cruciate ligament and posterior horn of lateral meniscus

  • Medially: Joint capsule and deep fibers of the medial collateral ligament (MCL)

  • Laterally: Intercondylar region, cruciate ligaments

Function

  • Acts as a shock absorber between femur and tibia

  • Provides joint stability, particularly resisting anterior translation of femur on tibia

  • Aids in load distribution and transmission across the knee

  • Lubricates and nourishes articular cartilage by facilitating synovial fluid flow

  • Contributes to proprioception within the knee joint

Clinical Significance

  • Medial meniscus tears are more common than lateral due to its firm capsular and MCL attachments

  • Commonly injured in twisting movements of the knee (especially with ACL injuries)

  • Degenerative tears occur in elderly patients with osteoarthritis

  • Tears may cause locking, clicking, or instability of the knee

  • Important consideration in knee arthroscopy and meniscal repair/transplantation

MRI Appearance

T1-weighted images:

  • Meniscus appears as a uniform low-signal (dark) triangular structure

  • Tears may appear as linear or complex hyperintense signal extending to the articular surface

T2-weighted images:

  • Normal meniscus remains low signal

  • Meniscal tears show bright hyperintense linear or complex signals extending to the meniscal surface

  • Paramensical cysts appear bright adjacent to tears

STIR (Short Tau Inversion Recovery):

  • Normal meniscus: low signal

  • Tears: bright hyperintensity

  • Adjacent edema or cysts also appear hyperintense

Proton Density Fat-Sat (PD FS):

  • Best for meniscus evaluation

  • Normal: low signal

  • Tear: bright linear or irregular signal within meniscus, reaching articular surface

T1 Fat-Sat Post-Contrast:

  • Normal meniscus does not enhance

  • Post-operative meniscus or inflammatory pathology may show mild enhancement

  • Scar tissue or granulation may enhance in meniscal repair site

3D T2 SPACE / CISS:

  • Meniscus appears as a dark crescentic structure

  • High-resolution imaging clearly defines tear patterns and meniscal morphology

  • Provides excellent multiplanar reconstructions for surgical planning

MRI Arthrogram Appearance

  • Contrast enters meniscal tears, appearing as bright hyperintense lines within the normally dark meniscus

  • Improves sensitivity for small, complex, or recurrent tears

  • Helps differentiate true tears from intrasubstance degeneration

CT Appearance

Non-Contrast CT:

  • Meniscus poorly visualized as a soft tissue density

  • Calcification or meniscal ossicles may be seen

  • Indirect signs include joint space narrowing or subchondral changes

Post-Contrast CT:

  • Limited role in direct meniscus evaluation

  • May demonstrate synovial enhancement or adjacent pathology

CT Arthrogram Appearance

  • Contrast outlines and enters meniscal tears

  • Abnormal contrast tracking within meniscus indicates tear

  • Provides detailed evaluation of tear morphology when MRI is contraindicated

MRI image

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

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

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medial meniscus sagittal cross sectional anatomy 3T MRI AI enhanced radiology anatomy image-img-00000-00000

CT image

medial meniscus ct sag image

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medial meniscus ct axial

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medial meniscus ct coronal image