Tissue Mechanics: Cartilage

Question 1

Where is articular (hyaline) cartilage found?

Answer 1

joints, growth plates

Question 2

Where is fibrocartilage found?

Answer 2

IV disks, mandibular condyles, meniscus

Question 3

Where is elastic cartilage found?

Answer 3

epiglottis, eustachian tube

Question 4

does cartilage function as a shock absorber?

Answer 4

NO

Question 5

what is teh function of cartilage?

Answer 5

• supports/transmits loads across mobile surfaces
• distributes joint loads over a wider area (stress reduction)
• stabilize and guide joint motion
• lines the ends of bones (prevents wear)
• lubrication reduces friction coefficient

Question 6

describe the composition of hyaline cartilage

Answer 6

water (58-78%)
chondrocytes (1%)
proteoglycans

Question 7

where is most of the water in cartilage found?

Answer 7

middle zone

Question 8

describe the orientation fo cartilage in its different layers.

Answer 8

superficial layer: parallel
middle layer: oblique
deep zone: perpendicular

Question 9

describe the proteoglycan content in cartialge

Answer 9

increases from surface till the middle zone and diminishes towards the deep zone
(so there is the most proteoglycan in the middle)

Question 10

the proteoglycan + collagen network limits flow of water in/out of the tissue

Answer 10

true

Question 11

what provides cartilage with its tensile strength?

Answer 11

type 2 collagen

Question 12

tissues with high proteoglycan content exhibit what properties?

Answer 12

• high water content
• low hydraulic permeability
• highly resists compressive stress
• damage to proteoglycans will result in increased water mobility and impaired mechanical function

Question 13

what happens to cartilage under tension?

Answer 13

-collagen fibers stretch along the axis of loading

Question 14

what does tensile modulus (stiffness) depend on?

Answer 14

• type/amount of collagen cross-linking
• density of collagen fibers
• orientation of collagen fibers
• tensile modulus is FLOW INDEPENDENT

Question 15

tensile modulus varies 5-25 MPa depending on what?

Answer 15

• location of joint surface
• depth of specimen
• orientation of specimen relative to joint surface

Question 16

what happens to cartilage under compressive force?

Answer 16

permeability decreases

Question 17

what is the response of cartilage to shear force?

Answer 17

stretching & deformation of the solid matrix. Deformation but

• no change in volume
• no pressure gradient
• no fluid flow thru the matrix

Question 18

for a 2-4mm human or bovine articular cartilage, how long does it take to reach creep equilibrium?

Answer 18

4-16 hours

Question 19

the higher the rate of loading results in what effect on cartilage?

Answer 19

more stress/more resistance

Question 20

what effect does OA have on cartilage metabolism?

Answer 20

imbalance of cartilage metabolism (anabolism/catabolism is disrupted)

Question 21

what effect does OA have on cartilage tensile and compressive stiffness?

Answer 21

both decrease

*fracture stress also decreases

Question 22

what does decreased tensile and compressive stiffness manifest as histologically and microscopically?

Answer 22

disorganized ECM (disrupted collagen and GAG network)

Question 23

what happens to hydraulic permeability with OA?

Answer 23

increases

Question 24

what are some predisposing factors to OA?

Answer 24

Immobilization, joint instability, overuse, trauma, injury, or obesity