Articular Cartilage Pathophysiology and Treatment

Question 1

what is the fluid portion of articular cartilage?

Answer 1

water and ions

Question 2

what is the solid portion of articular cartilage?

Answer 2

collagen and proteoglycans

Question 3

t/f: adult cartilage is separated from subchondral vascular spaces by the subchondral plate

Answer 3

true

Question 4

what does cartilage being avascular mean for the tissue?

Answer 4

it has low metabolic activity and poor regenerative capabilities

Question 5

what are some characteristics of articular cartilage?

Answer 5

biphasic material

avascular

viscoelastic

time dependent behavior when subjected to deformation

low permeability

Question 6

solid phase has ____ resistance to flow, causing _____interstitial pressure

Answer 6

high, high

Question 7

what is the role of proteoglycans and fluid in articular cartilage?

Answer 7

they help provide compressive resistance

Question 8

what allows fluid and waste to leave articular cartilage?

Answer 8

loading

Question 9

what allows fluid and nutrients to enter the articular cartilage?

Answer 9

unloading

Question 10

what are the zones of articular cartilage?

Answer 10

superficial tangential zone

middle (transitional) zone

deep zone (radiate stratum)

tidemark

Question 11

what is the superficial tangential zone of articular cartilage?

Answer 11

densely packed type 2 collagen fibers arranged parallel to the surface that make up 10-20% of total thickness

Question 12

what is the middle (transitional) zone of articular cartilage?

Answer 12

random orientation of fibers that are further apart create an open meshwork of cartilage that gives it the ability to absorb compressive forces

30% total thickness

Question 13

what is the deep zone (radiate stratum) of articular cartilage?

Answer 13

fibers that form larger, radially-oriented fiber bundles perpendicular to the surface

40-60% total thickness

Question 14

what is the tidemark of articular cartilage?

Answer 14

interface b/w articular cartilage and calcified cartilage beneath it that anchors cartilage to bone

Question 15

what is the articular cartilage response to compression?

Answer 15

fluid gets pushed out to get rid of waste and fluid is recovered post stress-removal

Question 16

what is the articular cartilage response to tension?

Answer 16

anisotropic response: stiffer in parallel
innomogenous response: stiffer in superficial region

Question 17

what is the articular cartilage response to shear?

Answer 17

no volume changes and no interstitial fluid flow

Question 18

how does articular cartilage receive its nutrition?

Answer 18

efflux and influx with loading and unloading

cartilage needs proper loading

Question 19

what are the factors that contribute articular cartilage degeneration?

Answer 19

magnitude of stresses

of sustained stress peaks

structural changes

mechanical changes

4 Fs of cartilage degeneration

Question 20

what are the 4 Fs of cartilage degeneration?

Answer 20

fissures result in fibrillation, flaking, and focal cysts

Question 21

what are fissures?

Answer 21

cracking in the cartilage

Question 22

what are fibrillations?

Answer 22

crack in the bone leaving flakey pieces hanging off the bone surface

Question 23

what are flakes?

Answer 23

detached fibrillation

Question 24

what is endochondral ossification?

Answer 24

replacement of calcified layer of articular cartilage

Question 25

what happens to articular cartilage in aging?

Answer 25

deeper layers of cartilage gradually replaced with bone and superficial cartilage becomes thinner w/micro-fracture there is possible formation of new ossification center that extends into the calcified layer of cartilage advancing into tidemark and thinning the non-calcified layer

Question 26

what is interfacial wear?

Answer 26

bearing surfaces in direct contact defects in cartilage increase permeability and less lubricating fluid is available

Question 27

what is fatigue wear?

Answer 27

microscopic damage w/in bearing material under repetitive stressing low load long time

Question 28

what is impact loading?

Answer 28

rapid application, high load insufficient time for internal fluid redistribution to relieve compacted region

Question 29

what is type 1 cartilage injury?

Answer 29

superficial microscopic damage to chondrocytes and ECM

Question 30

what is type 2 cartilage injury?

Answer 30

partial thickness microscopic disruption of articular cartilage surface chondral fractures and fissures poor prognosis bc of no inflammatory response due to not penetrating the subchondral bone

Question 31

what is type 3 cartilage injury?

Answer 31

full thickness disruption of articular cartilage and penetration of subchondral bone produces significant inflammatory process (OA)

Question 32

the onset of OA increases with _____ and typically affects _____ _____ joints

Answer 32

age, weight bearing

Question 33

what are the clinical signs of cartilage injuries?

Answer 33

impaired mobility, muscles performance, and balance activity limitations participation restrictions

Question 34

incapacity depends on what 2 things?

Answer 34

extent of damage and comorbidities

Question 35

where are the most common meniscal injuries?

Answer 35

TMJ and knee

Question 36

is an outer knee tear repairable?

Answer 36

no!

Question 37

tear tears in the midsection of the knee repairable?

Answer 37

possibly is vascularity is stimualted

Question 38

when does cartilage not heal?

Answer 38

when it doesn't penetrate the subchondral bone

Question 39

when the subchondral bone is penetrated, is there repair?

Answer 39

yes!

Question 40

what is hoop stress of cartilage?

Answer 40

the way it handles stresses direct pressure causes a resistance in the form of hoop stress

Question 41

is repaired articular cartilage the same as the original cartilage?

Answer 41

no, it is different biochemically and biomechanically

Question 42

how many months does it take for 1/2 full thickness tears to degrade into fibrillation, fissuring, and extensive degeneration?

Answer 42

6 months

Question 43

what is the main treatment for cartilage injuries?

Answer 43

pharmacological management with NSAIDS, opioid analgesics, and intraarticular corticoid injections

Question 44

how is a medial unicompartmental knee injury usually treated?

Answer 44

unloading braces that offloads the medial compartment

Question 45

what are common cartilage injury treatments?

Answer 45

pharmacological management unloading intraarticular viscosupplementation injections (chicken shots) surgical management PT

Question 46

what does PT do to treat cartilage injuries?

Answer 46

decrease joint pain improve ROM improve function modalities patient education impact aerobic exercise strengthening

Question 47

what is osteochondritis dissecans?

Answer 47

a rare anterior knee and ankle pain (can be other joints as well)

Question 48

how is knee osteochondritis dissecans characterized?

Answer 48

WB medial and lateral femoral condyles pain and catching sensation with knee flexion extensor weakness maltracking of tibiofemoral joint painful arc in smaller lesions where it passes over articular surface

Question 49

how is ankle osteochondritis dissecans characterized?

Answer 49

the dome of the talus pain in anterolateral and posteromedial ankle

Question 50

how is osteochondritis dissecans diagnosed?

Answer 50

MRI, bone scan, or CT

Question 51

when would conservative treatment of osteochondritis dissecans be used?

Answer 51

if the lesion remains intact

Question 52

when would there be surgical intervention for osteochondritis dissecans?

Answer 52

if there is a need to reattach loose fragments to bone

Question 53

what is micro-fracture surgery?

Answer 53

when a surgeon uses a pick or drill to make small holes into the subchondral bone of areas of breakdown to create bleeding, trigger inflammation, and therefore fibrocartilage growth

Question 54

what kind of cartilage is created by microfracture surgery?

Answer 54

fibril cartilage which isn't ideal but may help relieve some symptoms

Question 55

is microfracture surgery better in WB or reduced WB surfaces?

Answer 55

reduced WB surfaces

Question 56

when is osteochondral autograft transplant indicated?

Answer 56

in symptomatic, unipolar lesions of the distal femoral condyles (as well as other joints) non degenerative joints joints with ligamentous stability and meniscus competence