Articular Cartilage Pathophysiology and Treatment Flashcards
what is the fluid portion of articular cartilage?
water and ions
what is the solid portion of articular cartilage?
collagen and proteoglycans
t/f: adult cartilage is separated from subchondral vascular spaces by the subchondral plate
true
what does cartilage being avascular mean for the tissue?
it has low metabolic activity and poor regenerative capabilities
what are some characteristics of articular cartilage?
biphasic material
avascular
viscoelastic
time dependent behavior when subjected to deformation
low permeability
solid phase has ____ resistance to flow, causing _____interstitial pressure
high, high
what is the role of proteoglycans and fluid in articular cartilage?
they help provide compressive resistance
what allows fluid and waste to leave articular cartilage?
loading
what allows fluid and nutrients to enter the articular cartilage?
unloading
what are the zones of articular cartilage?
superficial tangential zone
middle (transitional) zone
deep zone (radiate stratum)
tidemark
what is the superficial tangential zone of articular cartilage?
densely packed type 2 collagen fibers arranged parallel to the surface that make up 10-20% of total thickness
what is the middle (transitional) zone of articular cartilage?
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
what is the deep zone (radiate stratum) of articular cartilage?
fibers that form larger, radially-oriented fiber bundles perpendicular to the surface
40-60% total thickness
what is the tidemark of articular cartilage?
interface b/w articular cartilage and calcified cartilage beneath it that anchors cartilage to bone
what is the articular cartilage response to compression?
fluid gets pushed out to get rid of waste and fluid is recovered post stress-removal
what is the articular cartilage response to tension?
anisotropic response: stiffer in parallel
innomogenous response: stiffer in superficial region
what is the articular cartilage response to shear?
no volume changes and no interstitial fluid flow
how does articular cartilage receive its nutrition?
efflux and influx with loading and unloading
cartilage needs proper loading
what are the factors that contribute articular cartilage degeneration?
magnitude of stresses
of sustained stress peaks
structural changes
mechanical changes
4 Fs of cartilage degeneration
what are the 4 Fs of cartilage degeneration?
fissures result in fibrillation, flaking, and focal cysts
what are fissures?
cracking in the cartilage
what are fibrillations?
crack in the bone leaving flakey pieces hanging off the bone surface
what are flakes?
detached fibrillation
what is endochondral ossification?
replacement of calcified layer of articular cartilage
what happens to articular cartilage in aging?
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
what is interfacial wear?
bearing surfaces in direct contact
defects in cartilage increase permeability and less lubricating fluid is available
what is fatigue wear?
microscopic damage w/in bearing material under repetitive stressing
low load long time
what is impact loading?
rapid application, high load
insufficient time for internal fluid redistribution to relieve compacted region
what is type 1 cartilage injury?
superficial
microscopic damage to chondrocytes and ECM
what is type 2 cartilage injury?
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
what is type 3 cartilage injury?
full thickness
disruption of articular cartilage and penetration of subchondral bone produces significant inflammatory process (OA)
the onset of OA increases with _____ and typically affects _____ _____ joints
age, weight bearing
what are the clinical signs of cartilage injuries?
impaired mobility, muscles performance, and balance
activity limitations
participation restrictions
incapacity depends on what 2 things?
extent of damage and comorbidities
where are the most common meniscal injuries?
TMJ and knee
is an outer knee tear repairable?
no!
tear tears in the midsection of the knee repairable?
possibly is vascularity is stimualted
when does cartilage not heal?
when it doesn’t penetrate the subchondral bone
when the subchondral bone is penetrated, is there repair?
yes!
what is hoop stress of cartilage?
the way it handles stresses
direct pressure causes a resistance in the form of hoop stress
is repaired articular cartilage the same as the original cartilage?
no, it is different biochemically and biomechanically
how many months does it take for 1/2 full thickness tears to degrade into fibrillation, fissuring, and extensive degeneration?
6 months
what is the main treatment for cartilage injuries?
pharmacological management with NSAIDS, opioid analgesics, and intraarticular corticoid injections
how is a medial unicompartmental knee injury usually treated?
unloading braces that offloads the medial compartment
what are common cartilage injury treatments?
pharmacological management
unloading
intraarticular viscosupplementation injections (chicken shots)
surgical management
PT
what does PT do to treat cartilage injuries?
decrease joint pain
improve ROM
improve function
modalities
patient education
impact aerobic exercise
strengthening
what is osteochondritis dissecans?
a rare anterior knee and ankle pain (can be other joints as well)
how is knee osteochondritis dissecans characterized?
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
how is ankle osteochondritis dissecans characterized?
the dome of the talus
pain in anterolateral and posteromedial ankle
how is osteochondritis dissecans diagnosed?
MRI, bone scan, or CT
when would conservative treatment of osteochondritis dissecans be used?
if the lesion remains intact
when would there be surgical intervention for osteochondritis dissecans?
if there is a need to reattach loose fragments to bone
what is micro-fracture surgery?
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
what kind of cartilage is created by microfracture surgery?
fibril cartilage which isn’t ideal but may help relieve some symptoms
is microfracture surgery better in WB or reduced WB surfaces?
reduced WB surfaces
when is osteochondral autograft transplant indicated?
in symptomatic, unipolar lesions of the distal femoral condyles (as well as other joints)
non degenerative joints
joints with ligamentous stability and meniscus competence
