Updated: 9/24/2018

Meniscus

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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) Humphrey Ligament
        • 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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Questions (4)
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(SBQ07SM.34) Which of the following is true when comparing the medial mensicus to the lateral meniscus? Review Topic

QID: 1419
1

More anterior translation with extension and less posterior movement with flexion

11%

(79/705)

2

Less anterior translation with extension and posterior movement with flexion

73%

(512/705)

3

More posterior translation with extension

4%

(25/705)

4

More anterior translation with flexion

7%

(46/705)

5

Less capsular attachments to the meniscus periphery

5%

(37/705)

ML 2

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PREFERRED RESPONSE 2
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