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ANAT2012 > Joints, Articular cartilage and Synovial fluid L3: Menisci- Aging, pathology & rehabilitation > Flashcards

Joints, Articular cartilage and Synovial fluid L3: Menisci- Aging, pathology & rehabilitation Flashcards

1
Q

What are the 6 functions of menisci?

A
  1. Load distribution decreases stress
    • Semi-lunar
    • Flat tibial plateau & round femoral condyles
    • Doubled contact by fibula
  2. Shock absorption
  3. Joint stability
    • Against translation
  4. Proprioception
    • Margins innervated feeback
  5. Lubrication
    • Compression released synovial fluid
  6. Protects articular cartilage
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2
Q

Gross structure of menisci

A
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3
Q

The medial meniscus is ______(longer/shorter) from AP than the lateral meniscus.

A

Longer

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4
Q

The medial meniscus has a ______(larger/smaller) posterior horn than the lateral meniscus.

A

Larger

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5
Q

The medial meniscus is ______(more/less) variable than lateral meniscus.

A

Less

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6
Q

The medial meniscus is ______(more/less) mobile than lateral meniscus.

A

Less When weight-bearing, it has the opportunity to move out of the way

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7
Q

Does the medial or the lateral meniscus cover more of the tibial plateau?

A

Lateral covers more

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8
Q

Why does the medial meniscus cover less of the tibial plateau?

A

The medial menicus proportionally covers less of facet because femur and tibia surfaces are also larger = greater weight bearing = less likely to move out of way = injury

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9
Q

Which menisci is more prone to injury?

A

Medial because… greater weight bearing = less likely to move out of way = injury

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10
Q

What is the composition of menisci?

A
  • Early development = all cells similar
  • Adult = outer zone – ‘fibroblast-like’ o Long cell extensions = communication! o Collagen Type I = 80% dry weight
  • = inner zone – ‘fibrochondrocytes’ o Collagen = 70% dry weight Type II > Type I
  • = superficial zone - progenitor cells o Decrease as age –? Less capacity to repair stem cells
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11
Q

What are the 3 characteristics of collagen alignment of menisci?

A
  1. Anisotropic
  2. Principal direction = circumferential
    • Type I fibres (strong outside)
  3. Radial fibres also present in midzone and especially on surface (tibial > femoral)
    • Radiating out from inner to outer rims are focused on tibia
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12
Q

What is the vascularisation and innervation of menisci?

A

Was vascularization at birth –> recedes to only 10-20% of outside

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13
Q

What is the vascularisation of menisci like?

A
  • • Birth = 100%
  • ~ 10 yrs = 10-30%
  • Adult = peripheral 10-25%
    • Tear in inner rim = poor ability to heal
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14
Q

What is the innervation of menisci?

A
  • Outer 1/3 vascular zone
  • Mechanoreceptor esp. horn
  • Proprioception
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15
Q

What are the biomechanics of menisci?

A
  • Compressive loading generates significant radial & circumferential stresses
  • flat surface –> load coming down through curved surface –> wedge shaped meniscus –> push meniscus outwards –> meniscal horns are attached to tibia –> weight bear –> tensile force –> radially directing out circumference –> radial fibres circumferential hoop stress
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16
Q

What happens in meniscal translation during movement?

A

Translate posteriorly and medially during joint loading (weight bearing)

17
Q

What is the ultimate tensile strength of menisci?

A
  • Relative to fibre alignment
    • Parallel 6.3-8MPa
    • Perpendicular <1MPa
  • Increases with age (cross-linkages)
18
Q

Modulus of elasticity. Which forces can menisci withstand? (most to least)

A

Tension > Compression > Shear

19
Q

What is ageing?

A

Earliest changes occurred predominantly along the inner rim

20
Q

Which horn is least affected by age and OA?

A

Anterior horns of both medial and lateral menisci

  • Surface roughness with severe fibrillation
  • Cellular senescence cell density
  • the appearance of acellular zones,
  • mucoid degeneration
  • collagen amount, fibril diameter & cross-link
21
Q

What are some characteristics of menisci from OA joints?

A
  • severe fibrocartilaginous separation of the matrix
  • extensive fraying
  • tears
  • calcification
  • abnormal cell arrangements included
    • decreased cellularity,
    • diffuse hypercellularity
    • cellular hypertrophy
    • abnormal cell clusters
22
Q

What are the 2 types of meniscal pathological tears? How are they different?

A
  1. Traumatic
    • Acute
  2. Degenerative
    • Accumulative, fatigue
23
Q

What are 3 types of diagnosis for meniscal pathology?

A
  1. Subjective & objective examination
  2. Arthroscopy = gold standard
  3. MRI sensitivity 93% MM &79% LM
    • specificity 88% MM & 96% LM
24
Q

What are the 6 ISAKOS classifications of meniscal tears?

A
  1. Depth 2. Location 3. Tear pattern 4. Longitudinal 5. Horizontal 6. Radial
25
Q

ISAKOS classifications of meniscal tears: What are the 2 types of depth classification?

A
  1. Partial
  2. Complete
    • complete from surface to surface or layers
      • superior to inferior
      • vertical (inner to outer)
26
Q

ISAKOS classifications of meniscal tears: What are the 2 types of location classification?

A
  1. Rim
    • circumferential zone 1,2,3
  2. Radial
    • Anterior
    • Middle
    • Posterior
27
Q

ISAKOS classifications of meniscal tears: Longitudinal

A

Vertical = superior to inferior (perpendicular to tibial plateau) - split between zone 1 and 2

  • Young athletic
  • +/- ACL
  • Zone 1 & 2
  • Posterior
  • Bucket-handle
    • meniscus is in the way- move jt around to get free
28
Q

ISAKOS classifications of meniscal tears: Horizontal

A

Parallel with tibial surface

  • Degeneration (usually older)
    • Split into inferior/superior
29
Q

ISAKOS classifications of meniscal tears: Radial

A
  • Most common type in young adults
  • At junction of 1/3s
  • Starts at inner rim (avascular and hyaline cartilage)
30
Q

What are the 3 rehabilitation options for meniscal pathology?

A
  1. Repair
  2. Menisectomy
    • more meniscus removed –> less contact area –> less shock absorption –> more stress on joint
    • Partial
      • try to only trim or repair
    • Complete
      • Increase 235%-335% increase in peak local contact load
  3. Tissue engineering
    • Autologous/allogeneic/exogeneic
    • Stem cell
31
Q

What are the 5 injuries that lead to damage of hyaline cartilage?

A
  1. Acute trauma
  2. Post-traumatic
  3. Prolonged overloading
  4. Prolonged immobilisation
  5. Local or systemic inflammation
32
Q

How does acute trauma lead to damage of hyaline cartilage?

A

primary injury due to impact force that can cause chondrocyte death, damage to collagen and loss of proteoglycans

33
Q

How does post traumatic injury lead to damage of hyaline cartilage?

A

secondary to ligamentous instability or meniscal damage or muscle imbalance –> altered joint kinematics

  • possible increased translation / recurrent instability / change in bearing area –> loading of unconditioned cartilage
  • post-heamarthrosis (as with ACL rupture) –> biochemical change to synovial fluid with possible negative effect on chondrocyte activity
34
Q

How does prolonged overloading lead to damage of hyaline cartilage?

A

e.g. chronic obesity –> fatigue failure, prolonged postures

35
Q

How does prolonged immobilisation lead to damage of hyaline cartilage?

A
  • decreased nutrition as a result of decreased synovial flow in/out of cartilage
  • decreased mechanical stimulus to the chondrocytes to maintain ECM
36
Q

How does local or systemic inflammation lead to damage of hyaline cartilage?

A

inflammatory markers (chemicals) affects chondrocytes –> produce proteolytic enzymes –> degradation of ECM

37
Q

What are the 4 factors affecting the ability of hyaline cartilage to repair?

A
  1. Avascularity – inability to heal via inflammatory response; decreased O2
  2. Low cellular density – greater relative portion of ECM to be maintained by each cell
  3. Low metabolic activity – low turnover of ECM
  4. Inability of chondrocytes to migrate to site of injury

ANAT2012 (31 decks)

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