3.1 - articular cartilage

• fibrous

• cartilaginous

• synovial (diarthrodial) 

what are the 3 types of joints? 

synovial

hyaline cartilage is a _________ type of joint

• distribute joint leads

• decrease friction

what are the 2 purposes of hyaline cartilage

biphasic

• collagen-PG solid matrix (25%)

• freely moving interstitial fluid (75%)

articular cartilage is made up of ________ material

chondrocytes 

the purpose of ______________ is to manufacture, secrete, and maintain organic component of extracellular compartment (the MATRIX) 

MATRIX

the ______________ provides the structural components supporting the internal mechanical stresses that results form loads being applied to the joint cartilage; it is these structural components, together with water, that determine the biomechanical behavior of the tissue

collagen fibrils; PG

the MATRIX = ___________ and ____________

90; flexion 

Peter Pidcoe extra fact:

by the time you hit ________ degrees of knee _________, the entire patella has hit the condyles at some point

collagen 

___________ is the most abundant protein in the body 

densely packed → less dense → radial orientation → grows into bone where it is anchored

how is the collagen distributed in this picture

• hyaline bone

• annular ligament

Peter Pidcoe extra fact:

where in the body does cartilage not attach to bone?

tension

collagen is stronger in (tension or compression)

anisotropic 

collagen is ___________ meaning it has different mechanical properties when loaded along different axes 

proteoglycan with bottle brush GAGs attached to protein core

what is this

glycosaminoglycan

GAG stands for

age

proteoglycans change with _________

10:1 → 2:1

(could be from cartilage maturation or result from increased functional demand) 

chondroitin sulfate - keratan sulfate ration is _________ at birth and _______ as an adult

water

_________ is the most abundant component of articular cartilage and is most concentrated near articular surface

70

_____% of the intermolecular space is water

avascular

articular cartilage is (vascular or avascular)

• load; pressure

• chondrocytes; synovial fluid

• mechanical; lubrication

the significance of water being in the intermolecular space is:

• free to move when _______ or ______ gradient applied

• permits diffusion of nutrients/waste products between _________ and ________

• also controls __________ behavior and joint __________

negatively; Na+ and Ca+; repulsive

GAGs are (positively or negatively) charged so they attract ________ and _________ molecules which increases the _________ force

more (becuase water want to leave to dilute the outside)

if there is (less or more) salt on the outside, it will decrease the stiffness of the GAG structure

• interstitial fluid flow

• intrinsic behavior of solid matrix

what are the 2 reasons behind articular cartilage being viscoelastic

• creep 

• stress relaxation 

what are the 2 material responses when articular cartilage is put under stress

creep

__________ is where a constant force is applied → rapid initial deformation then slow to equilibrium

stress relaxation

______________ is where a constant deformation (or position) is applied → high initial stress then decreased stress

fluid flow (exudate); solid matrix

_________ controls creep and in equilibrium _________ supports the load

A to B

what points indicate the copious fluid exudation 

C

what point indicates no exudation

creep elongates progressively overtime, compressive load goes from 0-100 BAM

difference between a compressive load graph and a creep deformation graph

joy to the world and give thanks to pidcoe

• unloaded

• creep

• equilibrium

indicate which image is showing

• creep

• equilibrium

• unloaded

exudation; redistribution 

the method behind stress relaxation is that stress rises due to fluid __________ and stress relaxes due to fluid ____________

more

Peter Pidcoe extra fact:

old cartilage has (less or more) permeability

less

Peter Pidcoe extra fact:

young cartilage has (less or more) permeability

the displacement increases at first and then stays at one dimension

stress relax will increase more before it relaxes, takes more time

what is the difference between the displacement graph and stress relaxation graph

low (this means it is hard to push liquid through) 

articular cartilage has (low or high) permeability 

harder (increases the frictional drag → makes tissue stiffer → difficult for fluid to move)

does a higher load on the joint articular cartilage make is easier or harder for fluid to move

low

fluid in the joint space is reabsorbed during the (low or high) load

pull out

the toe region of the stress strain graph is due to collagen fiber “__________”

dec; inc (essentially means that pH can affect cartilage so lay off the salt)

increased water content leads to (dec or inc) compressive strength and (dec or inc) permeability 

inc

if there is (dec or inc) permeability, this means that the structure has decreased ability to support loads

• collagen-PG matrix changes with age

• repetitive and massive movement of interstitial fluid may cause PG “washout”

• cumulative stress of impact loading (low or high)

• excessive stress concentrations int eh body (hot spots, too much at one spot)

4 causes of collagen network disruption

• congenital acetabular dysplasia 

• slipped capital femoral epiphysis

• intra-articular fx 

• meniscectomies → modify load pattern 

• ligament rupture → allows excessive movement and abnormal stresses 

• RA and joint space hemorrhage (hemophilia) can contribute to a breakdown in collagen-PG matrix integrity 

what are 6 examples of excessive stress concentrations in the body that can lead to collagen network disruption