Look at own right knee and draw from top down perspective
LM β Smaller semicircular shape. Anterior horn adjacent to ACL, posterior horn anterior to MM. Has Humphrey (anterior to PCL) and Wrisberg ligaments. No coronary ligament. Has recess for popliteal tendon. No attachment to LCL or joint capsule.
MM β Larger C-shaped structure. Anterior horn anterior to ACL, posterior horn anterior to PCL. Has coronary ligaments (making it less mobile). Firmly attached to joint capsule and deep MCL.
Anteriorly connected by intermeniscal (transverse) ligament
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Draw the cross section of fibers
3 layers:
Surface: parallel fibers
Superficial: oblique fibers
Deep: circumferential fibers that provide hoop stresses
"Hoop stress"
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What are hoop stresses in the meniscus?
The arrangement of collagen fibers in the meniscus convert axial compressive forces into a radially directed (tension) force, which is distributed and resisted as hoop stresses within the meniscus.
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Contents of meniscus?
Type 1 collagen 90% = fibrocartilage
10% - proteoglycans and elastin
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Blood supply of meniscus? Progression from embryo?
Lateral, middle and genicular arteries from popliteal artery β Perimeniscal Capillary Plexus (PCP)
Embryological blood supply: at birth completely vascularized β by 9 months avascular central third β devascularization continues until 10 years old
Described with 3 zones:
White-white zone - inner avascular
Red-white zone
Red-red zone - peripheral vascular
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To what extent is each meniscus vascularized?
Lateral meniscus: 10-25%
Medial meniscus: 10-30%
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Innervation of meniscus?
Only peripheral 2/3innervated by type 1 (proprioception) and type 2 (touch and pressure) nerve endings
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Function of meniscus?
Load transmission: increases contact surface area with femur (50% goes through meniscus)
Shock absorption - half the stiffness of cartilage, making it more elastic
Articular conformity
Knee joint stability - especially in absence of ACL, MM provides AP stability
Lubrication via sponge phenomenon - participates in boost and weeping lubrication
Proprioception due to nerve endings
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What happens in meniscectomy?
1984 Fairbanks Seminal paper
Records changes in knee joint up to 14 years after meniscectomy
Found narrowed joint space and flattening of femoral condyle after meniscectomy
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Where else can we find meniscus-like structures?
ACJ, SCJ, TFCC
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