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Updated: May 16 2022

Meniscus

Images
https://upload.orthobullets.com/topic/9019/images/Meniscus Anatomy JPG_moved.jpg
https://upload.orthobullets.com/topic/9019/images/humphrey lig_arrow.jpg
  • Function
    • Force transmission
      • the meniscus functions to optimize force transmission across the knee. It does this by
        • increasing congruency
          • increases contact area leads to decreased point loading
        • shock-absorption
          • the meniscus is more elastic than articular cartilage, and therefore absorbs shock
        • transmits 50% weight-bearing load in extension, 85% in flexion
    • Stability
      • the meniscus deepens tibial surface and acts as secondary stabilizer
        • medial meniscus
          • posterior horn of medial meniscus is the main secondary stabilizer to anterior translation
        • lateral meniscus
          • is less stabilizing and has 2X the excursion of the medial meniscus
      • the menisci become primary stabilizers in the ACL-deficient knee
  • Composition
    • Made of fibroelastic cartilage
      • interlacing network of collagen, proteoglycan, glycoproteins, and cellular elements
      • composed of 65-75% water
    • Collagen
      • 90 % Type I collagen
    • Fibers
      • composed of two types of fibers which allow the meniscus to expand under compressive forces and increase contact area of the joint
        • radial
        • longitudinal (circumferential)
          • help dissipate hoop stresses
          • vertical mattress captures
  • Anatomy
    • Gross Shape
      • medial meniscus
        • C-shaped with triangular cross section
        • avarage width of 9 to 10mm
        • average thickness of 3 to 5mm
      • lateral meniscus
        • is more circular (the horns are closer together and approximate the ACL)
        • covers a larger portion of the articular surface
        • average width is 10 to 12mm
        • average thickness is 4 to 5mm
    • Attachment
      • transverse (intermeniscal) ligament
        • connects the medial and lateral meniscus anteriorly
      • coronary ligaments
        • connects the meniscus peripherally
        • medial meniscus has less mobility with more rigid peripheral fixation than the lateral meniscus
      • meniscofemoral ligament
        • connects the meniscus into the substance of the PCL
        • originate from the posterior horn of the lateral meniscus and has two components
          • Humphrey ligament (anterior)
          • Ligament of Wrisberg (posterior)
    • Blood supply
      • middle genicular artery
        • supply to posterior horns
      • medial inferior genicular artery
        • supplies peripheral 20-30% of medial meniscus
      • lateral inferior genicular artery
        • supplies peripheral 10-25% of lateral meniscus
        • central 75% receive nutrition through diffusion
    • Innervation
      • peripheral two-thirds innervated by Type I and II nerve endings
      • posterior horns have highest concentration of mechanoreceptors
  • Injury & Healing potential
    • See topic Meniscal Pathology
    • Tears in peripheral 25% red zone
      • can heal via fibrocartilage scar formation
        • fibrochondrocyte is cell responsible for healing
        • peripheral tears < 4 mm have best healing potential
    • Tears of central 75%
      • have limited or no intrinsic healing ability
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