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Meniscus


http://www.wheelessonline.com/image4/tib6a.jpg - Discussion: 
    - semilunar cartilages are extensions of tibial articulation of knee;
 
    - w/o menisci, tibial articulation is incongruous with the femur; 
    -
 microscopic features
    -
 vascular anatomy: 
    -
 anatomy: 
           -
 medial meniscus 
                  -
 bucket handle meniscus tear: 
                  -
 posterior horn tears of medial meniscus: 
           -
 lateral meniscus 
                  -
 discoid meniscus 
    -
 load bearing function: 
           - menisci distribute forces throughout underlying articular cartilage, thus minimizing point contact;
 
           - menisci bear 40 to 50% of the total load transmitted across joint in extension and 85% of the 
             compressive load is transmitted through the menisci at 90 deg of flexion;
 
    -
 motion characteristics: 
           - meniscal motion allows maximal congruency during knee flexion and helps to protect the mensici from injury;
 
           - in the study by V. Vedi et al (JBJS Vol 81-B Jan 1999), meniscal movement was studied using a dynamic MRI:
 
                 - w/ wt bearing, anterior horn of medial meniscus moved through a mean of 7.1 mm and posterior horn through
                   3.9 mm, and there was
3.6 mm of mediolateral radial displacement; 
                 - w/ wt bearing, the anterior horn of the lateral meniscus moves 9.5 mm and the posterior horn moves 5.6 mm,
                   and there was 3.7 mm of radial displacement;
 
                 - the authors felt that the relative immobility of the posterior horn of the medial mensicus may account for its
                   propensity for injury;
 
    - while secondary stabilizer, menisci do impart some stability to normal knee and more important to the ligament
      deficient knee;
 
    - each is attached at its periphery to capsular ligament on medial or lateral side of joint & at its horns to interarticular area
      of tibia;
 
    - connecting menisci anteriorly is the transverse ligament.
 
    - menisci help compensate for incongruence of the bones, and they appear to be involved in rotation by moving on the tibia;
 
    - as result of sufficient stress (usually rotary in wt-bearing, flexed knee), either meniscus may be torn w/in itself or
      from its peripheral attachment; 

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