Poth 434 - Meniscus Of The Knee - Mcgill

Front 1

Difference between medial and lateral

Back 1

medial: half circle, wider posteriorly, bigger diameter
lateral: full circle, same width all around, bigger coverage (more direct contact with articular cartilage on medial surface)

Front 2

ligament attachments

Back 2

-Coronary ligaments: attach the inferior edges of the menisci to the tibial plateau (medial meniscus is more firmly attached)
-Transverse: attaches anterior horns together
-MCL: achores deep portion of medial meniscus to tibia
Lateral meniscus is attached to: tendon of popliteux and meniscofemoral ligaments(ligaments of humphrey and Wrisberg)

Front 3

structure

Back 3

1)fibrocartilage
2)Collagen: Type I at periphery, Type II deep, type VI in spaces of type I. Organized in 3 layers

Front 4

3 layers of collagen framework

Back 4

1) Superficial: meshwork of fine fibrils, peripheral
2) Surface: meshwork of disorganized collagen bundles, deep to superficial
3) Middel: deepest layer, organized larger and coarser fibers
a) Circumferential: organized following C-shape of meniscus, resist hoop stress created by compression of the meniscus
b) Radial: radial oriented fibers ensure structural rigidity and resist longitudinal splitting

Front 5

Vascular Supply

Back 5

peripheral 1/3rd at best
arise from perimeniscal capillary plexus of lateral and medial geniculate arteries

Front 6

Innervation

Back 6

Found at peripheral 1/3
-most innervation at horns: more in posterior
-myelinated and unmyelinated
-Type I, II, III, mechanoreceptors

Front 7

Nutrition

Back 7

A) Periphery: Vasculature
b) Avascular part
1) Diffusion: marginal to central core due to dense, fibrous extracellular matrix
2) Intermittent loading (mechanical pumping)

Front 8

Mechanical properties

Back 8

1) Fibrocartilage: biphasic medium
2) Compression: LOW STIFFNESS (very compliant,) and LOW PERMEABILITY (so hard for fluid to flow out, so flow-dep. resistance helps to support compressive loads)
3) Tension: circumferential fibers resist hoop stress, NON-LINER, ANISOTROPIC and HETEROGENEOUS, highest tensile module in lateral meniscus posterior horn
4) Shear: LOW SHEAR MODULUS (allows for more deformation and keep congruency as joint moves. But because it is a viscoelastic tissue; rapid loading = stiffer = less deformable = horizontal and longitudinal tears)

Front 9

Shock absoprtion

Back 9

Responsible for 20% of shock absorption at knee

Front 10

Proprioception

Back 10

mechanoreceptors provide CNS with joint position information and provide a prioprioreceptive refles arc, contributing to dynamic muscular stabilization

Front 11

Joint stability

Back 11

only helps when ACL is gone but medial meniscus is still intact

Front 12

Joint lubrication

Back 12

allows uniform pressure on joint + improves congruency of joint = promotes viscous hydrodynamic action requires for full fluid-film lubrication

Front 13

Meniscal motion

Back 13

-lateral moves more than medial, so less likely to injure lateral
-permits to follow movement of knee
-anterior horn moves more than posterior

Front 14

Plant and twist injury

Back 14

ACL
MCL
medial meniscus

Front 15

Load bearing and transmission

Back 15

Extension: 50% of load
Flexion: 85% of load
if remove complete meniscus will decrease 50% contact area
if remove partially menisci, will increase contact pressure over 350%

Front 16

Injury

Back 16

5 times more likely to injure medial than lateral
-common = plant and twist mechanism

Front 17

Types of meniscal tears

Back 17

-longitudinal vertical: bucket handle (linked to repeted trauma and skeletal immaturity), traumatic
-radial: degenerative

Front 18

Healing

Back 18

Vascular regions: slow recovery so at high risk of reinjury for very long time
avascular regions: poor to no healing. 3 surgical options
a) partial menisectomy
b)manipulatiopn of capillary plexus
c)exogenous fibrin clots