Cartilage

Question 1

The nose and ear are made up of what kind of cartilage?

Answer 1

Elastic cartilage

Question 2

What structures are composed of fibrocartilage?

Answer 2

1 - iliac surface of SI joint
2 - menisci of the knee
3 - annular fibers of the disc

Question 3

Function of joint cartilage (2)

Answer 3

1 - decrease contact stress by spreading load over a larger area
2 - allow movement of articular surfaces with minimal wear and friction

Question 4

Can hyaline cartilage heal quickly? Why or why not?

Answer 4

No, because there is no nerve supply, no blood supply, no lymph supply.

Question 5

What are the components of cartilage?

Answer 5

Solid matrix
Chondrocytes
Water

Question 6

The solid matrix of cartilage is composed of what?

Answer 6

60% collagen and 40% proteoglycan gel

Percentages are by weight

Question 7

Function of collagen (2)

Answer 7

1 - provides ultrastructure for cartilage
2 - provides tensile stiffness and strength

Note: cartilage undergoes compression; collagen resists tensile load — collagen helps cartilage do its job by resisting tensile load

Question 8

Why is collagen better suited (compared to cartilage) in resisting tensile loads rather than compressive?

Answer 8

?

Loading of tensile force makes the fibers straighten.

Question 9

How is collagen arranged in zone 1?

Answer 9

Superficial zone: thickest zone. Random packed, random orientation in planes parallel to the surface

Question 10

How is collagen arranged in zone 2?

Answer 10

Middle zone — least amount of thickness. Random orientation and loosely packed.

Question 11

How is collagen arranged in zone 3?

Answer 11

Deep zone — medium amount of thickness. Perpendicular ordination, anchor to bone and fibrocartilage.

Question 12

The proteoglycan gel is composed of (2)

Answer 12

1 - Protein core

2 - Aggrecans

Question 13

What are aggrecans composed of and how do they help establish sponge model?

Answer 13

Aggrecans are negatively charged so they repulse/resist each other. This makes an inherent stiffness. It’s the anions that stiffens the Proteoglycan Gel and resists compression.

Question 14

How does water move to protect joints?

Answer 14

1 - proteoglycan gel attracts cations and sets up osmotic pressure

2 - cations osmotically draw water molecules into cartilage

So the cartilage stiffens and swells due to A) the repulsive force of aggrecans and B) the osmotic pressure attracting water

Under stress:
A- water squeezed out
B- produces increased swelling pressure (osmotic pressure)
C- equilibrium is re-established when swelling pressures balances the stress

Question 15

What zone is most of the water located in the cartilage? and why is this important?

Answer 15

Superficial zone (zone 1).

That means 70% of the water is free to move

Question 16

Most of the creep in cartilage is due to what?

Answer 16

Exudation of fluid

Question 17

What is the speed of creep as it applies to cartilage? Under a constant load…

Answer 17

Viscoelastic material deforms quickly at first and then more slowly over time until equilibrium is met

Question 18

What is the syringe effect?

Answer 18

With a slow load, more fluid comes out

With a fast load, there is resistance of fluid movement.

Question 19

How does cartilage behave in high speed loading?

Answer 19

Little deformation.

Because, syringe effect: not enough time to squeeze water out of tissue, therefore cartilage is very stiff.

E.g. discs = good shock absorbers

Question 20

How fast is the restoration when you unload after a slow load?

Answer 20

1 - Immediate restoration to 90% via elastic recoil
2 - Slower restoration via swelling pressure

E.g. being on your feet all day: take a seat and you’ll restore 90% thickness nearly immediately

Question 21

What kind of fluid acts as lubricant between articular surfaces?

Answer 21

Synovial fluid

Question 22

Name 2 types of lubrication

Answer 22

Fluid film

Boundary

Question 23

What is fluid film lubrication?

Answer 23

Thick film of lubricant that separates surfaces and occurs in physiologic loading

Question 24

Types of fluid film lubrication (2)

Answer 24

Hydrodynamic

Squeeze film

Question 25

What kind of fluid film lubrication creates a lifting action that keeps surfaces apart and reduces friction?

Answer 25

Hydrodynamic lubrication

Question 26

What kind of fluid film lubrication happens on non-parallel surfaces and with tangential movement?

Answer 26

Hydrodynamic lubrication

Question 27

What kind of fluid film lubrication is sufficient for high loads for short durations?

Answer 27

Squeeze lubrication

Question 28

What kind of fluid film lubrication are perpendicular force? And the viscosity holds the lubricant together so that it doesn’t escape from between the surfaces.

Answer 28

Squeeze lubrication

Question 29

What kind of lubrication is good in “severe loading” and is when monolayer of synovial fluid absorbs to surfaces?

Answer 29

Boundary lubrication

Question 30

The unwanted removal of material from solid surfaces by mechanical action

Answer 30

Cartilaginous wear 2 types: interfacial wear and fatigue wear

Question 31

What kind of cartilage wear happens from interaction of articular surfaces and is unlikely in healthy cartilage because of effective lubrication?

Answer 31

Interfacial wear

Question 32

What are 5 qualities of Interfacial wear?

Answer 32

``` By adhesion and abrasion Wear produces surfaces defects Softening and increased permeability Fluid leakage Loss of lubrication (into defects in the surface) ```

Question 34

What kind of cartilage wear occurs with repetitive cyclic loading (and the reloading occurs before cartilage has time to fully re-imbibe)?

Answer 34

Fatigue wear

Question 35

What type of cartilage wear involves repetitive stress on matrix, collagen fiber disruption, proteoglycan macromolecule disruption and microstructural disruption that leads to degeneration?

Answer 35

Fatigue wear Note: repetitive exudation and imbibition may “wash out” degraded proteoglycan gels

Question 36

What occupations lead to cartilage injury because of high repetitive loads?

Answer 36

Football player’s knees and ballet dancer’s ankles (high repetitive loads)

Question 37

Loss of muscle balance can led to cartilage injury because:

Answer 37

Loss of flexibility prevents loads from being evenly distributed through joint surface

Question 38

“Pebble in a shoe” defect focuses load into one area and can lead to cartilage injury. How might this happen (4)?

Answer 38

Intra-articular fracture Meniscectomy Slipped femoral epiphysis Ligamentous instability

Question 39

Disease that can lead to cartilage injury though matrix destruction include:

Answer 39

RA Joint space hemorrhage Collagen disorders

Question 40

Immobility can lead to cartilage injury because of

Answer 40

Decreased synovial fluid circulation

Question 41

Rapid high impact loads may not allow fluid to redistribute rapidly enough, causing high internal fluid pressure at the PG-collagen matrix (what kind of cartilage wear is this?)

Answer 41

Fatigue wear