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ANAT2012 > Joints, articular cartilage and synovial fluid L1: Biomechanics of cartilage and synovial fluid > Flashcards

Joints, articular cartilage and synovial fluid L1: Biomechanics of cartilage and synovial fluid Flashcards

1
Q

What is kinematics?

A

Describes the motion of objects

  • No reference to mass of object or force which causes motion
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2
Q

In most synovial joints, there is a comination of ____ and ____. Example: abduction of GHJ and tibiofemoral joint

A

Rotation and translation

  • Eg. Abduction of GHJ
    • Superior translation
    • Rotation
  • Eg. tibiofemoral joint
    • Rot and trans. Discrepancy in articular surfaces
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3
Q

Whaat is the instaneous centre of rotation (ICR)?

A
  • “the theoretical axis (centre) of rotation at a specific joint position”
    • At a specific moment in time
  • Rotation &; translation occur stimultaneously –> Axis (CoR) is moving
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4
Q

What are 2 examples of external force?

A
  1. Gravity
  2. ground reaction force
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5
Q

What are 2 examples of internal force?

A
  1. Active contractions from muscles
  2. passive resistance
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6
Q

Is force linear or angular?

A

Linear

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7
Q

Is moment linear or angular? What is the moment?

A

Angular

Force x distance (moment arm- perpendicular distance from CoR to line of action)

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8
Q

What is friction?

A

Frictional forces resist the movement of an object

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9
Q

What are the 4 features of synovial joints?

A
  1. Graduated flexibility
  2. Variable bearing area
  3. Articular cartilage
  4. Synovial fluid
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10
Q

How is graduated flexibility related to synovial joints?

A
  • Articular cartilage –> spongy bone –> compact bone (stiffness)
  • Diaphysis = compact bone
  • Epiphysis = spongy bone
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11
Q

How is variable bearing area related to synovial joints?

A
  • When jts move, muscles apply compression
  • Contact area, where force is going across, affects stress
  • Stress = force/area o EG. habitual postures
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12
Q

How is articular cartilage related to synovial joints?

A
  • Hyaline cartilage (most jts)
  • Fibrocartilage (ACJ and pubic symphysis)
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13
Q

How is synovial fluid related to synovial joints?

A

Nutrition

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14
Q

(Increased/decreased) co-efficient due to jt surface (smooth, quality of surface shape, amount of co-contraction) = (Increased/decreased) frictional force

A

Increased

Increased

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15
Q

Hyaline cartilage cells (chondrocytes) are in ______. (Sparse/dense)

A

Lacune sparse

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16
Q

Hyaline cartilage has _______ (highest/lowest) cell density.

A

Lowest

Poor ability to repair

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17
Q

Hyaline cartilage is ______ (vascular/avascular)

A

Avascular

Poor ability to repair

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18
Q

Dense regular connective tissue proper (DRCTP) is ______ (dense/sparse).

A

Dense

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19
Q

Dense regular connective tissue proper (DRCTP) is ________ aligned.

A

Regularly

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20
Q

Dense regular connective tissue proper (DRCTP) are made up of ___blasts and ____cytes.

A

fibroblasts

fibrocytes

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21
Q

Fibrocartilage is a combination of _________ and _________.

A

Connective tissue proper

Hyaline

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22
Q

What is an example of fibrocartilage

A
  • Meniscus
  • Pubic symphysis
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23
Q

Comparison between hyaline cartilage and fibrocartilage: Type of cell

A

H: Chondrocytes

F: Chondrocytes and fibrocytes

24
Q

Comparison between hyaline cartilage and fibrocartilage H20

A

H>F

70-85% : 60-70%

25
Q

Comparison between hyaline cartilage and fibrocartilage: Collagen

A

H: Type II

F: Type I

Both 15-20% by mass

75% dry weight

26
Q

Comparison between hyaline cartilage and fibrocartilage: Fibre orientation

A

H

Superficial: parallel

Middle: random

Deep: perpendicular

F

AF: circumferential

Meniscus: circumferential and radial

27
Q

Comparison between hyaline cartilage and fibrocartilage: Proteogylcan

A

H> F

<10% : 1-2%

28
Q

Collagen structure resists ____ forces.

A

Tensile

29
Q

The collagen structure depends on ____ they are made of and ________.

A

Substance

cross-sectional area

30
Q

The shape of cross-section of collagen is ____ and _____.

A

Immaterial

Simple

31
Q

Collagen structure is 4-10 times stronger than it needs to be. This is called ______.

A

Safety factor

  • What it needs to withstand vs what it can withstand
  • Subdivision- failure in one area doesn’t mean failure in all
32
Q

Collagen structure is hellical. True or false?

A

True

Bundle together fibrils

33
Q

Collagen structure has a staggered offset. True or false?

A

True

34
Q

What is a proeogylcan?

A

A protein core wth side chains of chondroitin sulfate ad keratin sulfate

35
Q

What is a proteoglycan aggregate?

A
  • Proteoglycans (green) bound to a hyaluronic acid backbone
  • Increased compression = increased resistance (-ve) = bottle brush shape (puff)
36
Q

How is the cartilage ECM created?

A
  • Repulsion of proteoglycan contained by collagen mesh-net
    • Pre-stressed
  • -ve charged ions attach ions (from synovial fluid) –> move into cartilage –> water flows in as well
37
Q

What is the tide mark?

A

Between calcified & non-calcified cartilage

38
Q

What is the fibre orientation of cartilage ECM?

A
  • Superficial = parallel (more collagen than proteoglycan)
  • Middle = random (more proteoglycan)
  • Deep = vertical (collagen)- anchor into calcified cartilage
39
Q

What are the 2 phases of the biphasic model of cartilage?

A
  1. Fluid phase
  2. Solid phase
40
Q

What is the fluid phase of the biphasic model of cartilage?

A
  • Fluid depends on rate of application of force
  • Eg. smack water vs slowly dip water
41
Q

What is the solid phase of the biphasic model of cartilage?

A
  • Cells
  • Collagen types I & II
  • Proteoglycans
42
Q

Solids that have ______ mechanical behaviour, because of a fluid-like component are ______.

A

time-dependent viscoelastic

  • Creep (constant load)
  • Stress relaxation (constant strain = stress)
43
Q

What are the 3 components that compression of the solid phase is resisted by?

A
  1. Viscous drag
  2. Electrostatic repulsion
  3. Osmotic swelling
44
Q

What is viscous drag and how does it resist compression of solid phase?

A
  • Resistance to flow
  • Water, synovial fluid = visocity
45
Q

What is electrostatic repulsion and how does it resist compression of solid phase?

A
  • Resist compression of cartilage
  • Maintain area = resolve deformation
46
Q

What is osmotic swelling and how does it resist compression of solid phase?

A
  • –ve proteoglycans –> attack +ve –> Water flows in
47
Q

What fibre type is best at withstanding force?

A

Type I

48
Q

Cartilage is _____ compliant than bone.

A

More

49
Q

What is permeability?

A

how easily fluid can move out

50
Q

Both hyaline and fibrocartilage have _____ permeability.

A

Low

51
Q

Hyaline cartilage can withstand _____ compressive forces than fibrocartilage.

A

More

Twice as much

52
Q

What is bearing?

A

A part of a machine that allows one part to rotate or move in contact with another part with as little friction as possible

53
Q

What is binding?

A

The action of fastening or holding together

54
Q

What are the 2 types of mixed lubrication?

A
  1. Fluid-film lubrication
  2. Boundary layer lubrication
55
Q

What is fluid-film lubrication?

A
  • Thin film of lubricant btn articular surfaces in contact
    • Load is supported by pressure developed in fluid
    • Fluid film needs to be >3x surface roughness
    • Viscosity is important (hyalonurate)
  • Pressurised fluid o Separates articular surfaces
    • Decreased co-effiecient of friction
56
Q

What is boundary layer lubrication?

A

• Surfaces are protected by a boundary lubricant (lubricin) • Prevent contact of articular surfaces

ANAT2012 (31 decks)

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