Meniscus
- 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;