Cartilage ageing

Question 0

What determines the mechanical behaviour of cartilage?

Answer 0

The ratio of water, collagen and proteoglycans

Question 1

What are the three components of cartilage?

Answer 1

Water, collagen and proteoglycans

Question 2

What does an increase in collagen do to the mechanical properties of collagen?

Answer 2

Increases cartilage stiffness

Question 3

What pathological change occurs in cartilage in OA?

Answer 3

Distribution of collagen fibres decreases the strength of the solid matrix increasing permeability leading to joint effusions

Question 4

What can cartilage thinning mean for a joint?

Answer 4

Predisposes to degenerative joint disease

Question 5

What is junk accumulation?

Answer 5

The proteolytic mediate of processing of proteoglycans with an increase in polydisperse population (MAP 1,3,1 and ADAMB 4 and 5) so there is larger variation in the sizes of particles

Question 6

What are the consequences of junk accumulation?

Answer 6

Altered activity of cells in response to junk proteins
Accumulation of junk degraded products
Decrease in fixed charge density due to a loss of proteoglycans

Question 7

What are the systems theories of aging?

Answer 7

Neuroendocrine and immunologic

Question 8

What are the cellular theories of ageing?

Answer 8

Free radicals or senscence/apoptosis/wear and tear

Question 9

What are the molecular theories of ageing?

Answer 9

Somatic mutation
Error catastrophe - random events at the molecular level drove the ageing process, proteins with errors degraded and replaced and if needed for genetic components will lead to further errors

Question 10

What are the evolutionary theories of ageing?

Answer 10

Antagonistic pleiotropy
Mutation accumulation
Disposable somatheory - natural selection means resources are invested in maintaining repair mechanisms until the organism has reproduced

Question 11

What ageing changes occur in osteoarthritis?

Answer 11

Secondary disease that can be explained by a primary trauma/condition, progression is influenced by ageing, not an inevitable consequence of ageing but risk increased by ageing

Question 12

What is joint congruency?

Answer 12

Articular cartilage thickness is inversely related to the congruence of the joint surfaces which equalises the stress in congruent and incongruent joints

Question 13

What is a congruent joint?

Answer 13

Small thickness of cartilage deforms a small amount but surface area is sufficiently large to distribute load

Question 14

What is an incongruent joint?

Answer 14

Large thickness of cartilage depresses so that the surface area under compression is sufficient to decrease the stress appropriately

Question 15

How are normal ageing mechanisms linked to OA?

Answer 15

Limitations placed on homeostatic mechanisms
Functional consequences are altered cellular activity (decreased chondrocyte proliferation, cellular senescence), altered ECM by calcification, increased mechanical stress to the cells and increased susceptibility to other risk factors