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Meniscus

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Other Names

  • Medial Meniscus
  • Lateral Meniscus
  • Menisci

Description

Meniscal anatomy and relationship to important structures of the knee joint[1]

General

  • Crescent-shaped wedges of fibrocartilage oriented circumferentially
  • Positioned between the tibial plateaus and the femoral condyles in the medial and lateral compartments
  • Menisci possess collagen fibers oriented circumferentially
  • These circumferential fibers are bound by radially oriented fibers

Structure

  • Made primarily of type I collagen bundles
    • Circumferential and radially oriented to help prevent tearing[1]
  • Contain types I and II neuroreceptors
  • Possible proprioceptive and mechanoreceptive capacities

Medial Meniscus

  • Larger of the two menisci
  • C-shaped and covers about 50% of the medial tibial plateau
  • Posterior horn is larger than anterior horn
  • Bony attachments to the anterior and posterior horns at the meniscal root
  • Peripherally, attaches to the joint capsule, deep fibers of the MCL
  • Providers anteroposterior stability to the knee
  • Stronger attachment to joint capsule, less mobile, more susceptible to separation and tears

Lateral Meniscus

  • More circular than the medial meniscus
  • Covers about 70% of the lateral tibial plateau
  • Posterior and anterior horns are similar in size
  • Anterior attachment next to the ACL
  • Posterior attachment behind intercondylar eminence, anterior to the attachment of the medial meniscus
  • It also has attachment to the PCL via meniscofemoral ligaments, popliteomeniscal fasculi and the ligament of Wrisberg
Illustration of the Watanabe classification of discoid meniscus. 1 (complete type), 2 (incomplete type), 3 (Wrisberg type)[2]

Discoid Meniscus

  • Congenital variant with abnormal morphology, can create innate instability of the lateral meniscus
  • Thicker, poor tissue quality, less vascularity than a normal meniscus
  • Prone to tears which can be symptomatic or asymptomatic

Watanabe Classification for Discoid Meniscus[3]

  • Type I/ Wrisberg
    • Least common, meniscotibial attachment of lateral meniscus is absent
    • Most unstable variation of discoid meniscus[2]
  • Type II/ complete
    • Most common type, meniscus covers the entire tibial plateau
    • Typically thickened and hypertrophic
  • Type III/ incomplete
    • More common than Type I, less common than Type II
    • partially covers tibial plateau, also thickened
    • Normal tibial attachment

Actions

Primary function[4]

  • Menisci transmits 50% of joint compressive forces in full extension
  • Approximately 85% of the load in 90° of flexion

Contribute to

  • Protect articular cartilage
  • Shock absorption
  • Augment lubrication
  • Rotation of the opposing articular surfaces
  • Joint nutrition
  • Tibiofemoral joint stability
  • Joint congruency
  • Proprioception[5]

Vascular Supply

Schematic drawing of the blood supply of the meniscus demonstrating the different vascular zones (RR is red, RW is red-white, WW is white)[6]
  • Distribution
    • The blood supply to the meniscus begins in the periphery which allows these regions to have the best healing
    • The outer third is considered red due to the good blood supply
    • The inner two thirds is considered white and is avascular, relies on synovial fluid for nutrition
  • Vascular classification
    • Based on the side of the tear they can be classified as white-white, red-red, or white-red.
    • Those tears in the white-white are avascular and typically do not heal.
  • Originates from geniculate arteries: superior, inferior, medial and lateral
    • Perimeniscal capillary plexus originating in the knee’s capsular and synovial tissues

Innervation

  • Needs to be updated

Clinical Significance


See Also


  1. 1.0 1.1 Torres, Stephen J., Jason E. Hsu, and Robert L. Mauck. "Meniscal anatomy." Meniscal Injuries: Management and Surgical Techniques (2014): 1-7.
  2. 2.0 2.1 Hirschmann, M. T., and N. F. Friederich. "Classification: discoid meniscus, traumatic lesions." The Meniscus (2010): 241-246.
  3. Chambers, Henry G., and Reid C. Chambers. "The natural history of meniscus tears." Journal of Pediatric Orthopaedics 39 (2019): S53-S55.
  4. Lee SJ, Aadalen KJ, Malaviya P, et al. Tibiofemoral contact mechanics after serial medial meniscectomies in the human cadavcadaveric knee. Am J Sports Med 2006;34(8):1334-1344.
  5. Zimny ML, Albright DJ, Dabezies E. Mechanoreceptors in the human medial meniscus. Acta Anat Basel 1988;133(1):35-40.
  6. van Schie, Peter, et al. "Intra-operative assessment of the vascularisation of a cross section of the meniscus using near-infrared fluorescence imaging." Knee Surgery, Sports Traumatology, Arthroscopy (2021): 1-10.
Created by:
John Kiel on 10 July 2019 00:00:52
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Last edited:
6 May 2024 14:07:53
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