cartilage and osteoarthritis Flashcards
what are some features of cartilage?
avascular, aneural, tissue with a low metabolic rate
does cartilage heal quickly or slowly?
slowly because avascular
what is cartilage designed to withstand?
rigorous loading without failure, to distribute loads, and to provide a low friction surface
what is articular cartilage made of?
zones
what does the tide mark mark?
the break between subchondral bone and calcified cartilage
what happens with aging in articular cartilage?
we wear away cartilage from the top down so more subchondral bone will be laid down as we age
what is the most unique AC material property as it relates to its mechanical beahvior?
fluid component
water content __________ and PG content _______ with increased depth of tissue
decreases, increases
why is it that the deeper we go in articular cartilage there is less water content?
because the pore size is smaller deeper
is water compressable?
no it squishes out
what is the solid component of articular cartilage?
porous, permeable matrix primarily of type 2 collagen and PG with an extremely low permeability coefficient (k)
what is the significance of split lines with tensions?
surgeons use them so they can suture in certain directions to avoid scaring
what materials display the same mechanical behavior despite the direction of forces?
isotropic (homogenous) ex) steel
T/F material properties of articular cartilage differ with direction of motion?
True
the solid component of articular cartilage is considered a _________ tissue?
anisotropic
T/F, joint mobs/non thrust manipulations do lengthen adaptively shortened tissue
False
the superficial fibers of AC are aligned _____ and the deeper fibers are aligned more ____
horizontally, vertical
AC visco-elastic mechanical behavior;
- Stress is developed in ____ - ___ solid matrix
- frictional drag is generated by ____ ___ flow
- greater PG concentraion = _____ elastic response/rupture strength
- aging ____ degree of PG aggregation
collagen-PG
interstitial fluid
increased
reduces
rate of creep is an indicator of tissue ______?
permeability
______ pores result in ______ Permeability and high friction to flow
small, low
what further reduces pore size?
compression
a low rate of creep = a low ______?
permeability
what is ideal mechanical behavior
we want high friction flow, low permeability, small pores, decreased creep rate
aging: ______ aggregation, _______ GAG content, and ______ chains
decreased, decreased, shorter
structural modifications may be linked to changes in what?
chondrocyte synthetic function
during a biphasic creep response in compression a rapid initial exudation of fluid comes from?
articular surface
what creates creep in a biphasic creep response in compression?
external compressive load
what is creep resisted by in a biphasic creep response in compression?
stress developed in collagen PG solid matrix and frictional drag
in a biphasic creep response in compression continued slower exudation until deformation equilibrium reached. external compressive load ultimately ______ stress developed in collagen-PG solid matrix alone
equals
what does the friction coefficient deal with?
shear force, compression decreases shear force
what does permeability coefficient go up with?
poor sizes
does a low or high permeability coefficient take longer to reach equilibrium?
low
during the biphasic stress-relaxation response stress is increased until what?
a given deformation is reached and then deformation/strain maintained
during the biphasic stress-relaxation response stress decreases under constant strain until what?
equilibrium stress is reached
in the biphasic stress-relaxation response what is fluid redistribution responsible for?
tissue stress relaxation
in the biphasic stress-relaxation response what does rapid redistribution of load throughout tissue reduce?
peak stresses and thus contributes to articular cartilage’s resilience
we load tissues until deformation but stress decreases with time because why?
bc of fluid redistribution
what re the 2 types of AC lubrication systems?
boundary and fluid
what is the boundary AC lubrication system?
each load bearing surface is coated with lubrication (diarthrodial joints)= 2 surfaces do not touch one another
when is the boundary AC lubrication system most effective?
at low loads
what is the fluid AC lubrication system?
a film of fluid interposed between 2 joint surfaces
what are examples of fluid AC lubrication systems?
hydrostatic, hydrodynamic, squeeze film, and elastohydrodynamic
what are the three aberrant lubrication systems?
adhesive wear, abrasive wear, and fatigue wear
what is adhesive wear?
osteochondritis dessicans
complete or incomplete separation of a portion of cartilage and bone
like post it notes
what is abrasive wear?
joint mouse irritation
like a stone in a shoe- annoyance
what is fatigue wear?
PG washout, aging, DJD
loss of PG matrix is caused by
prolonged immobilization, some anti-inflammatory drugs, trauma/sx, infection and/or as a normal component of aging
T/F loss of PG matrix is permanent?
False it may be reversible dependent upon degree and duration
what do NSAIDs do to PG content?
decrease it
what occurs in the early stages of development of osteoarthritis?
fraying of collagen bundles in superficial layer
why do we normally see rapid progression once fraying has begun in the development of osteoarthritis?
due to fiber orientation (the deeper layers are perpendicular so easier to knock down)
T/F shear force is not optimal once you get rid of the superficial layer?
true
what is chondromalacia?
softening of cartilage
what layers does tissue degeneration in chondromalacia appear to begin in?
3 and 4
T/F it is easy to to visualize tissue degeneration in chondromalacia early on?
no because it doesnt appear until layers 3 and 4. generally determined by palpation
