Cartilage ageing Flashcards
What determines the mechanical behaviour of cartilage?
The ratio of water, collagen and proteoglycans
What are the three components of cartilage?
Water, collagen and proteoglycans
What does an increase in collagen do to the mechanical properties of collagen?
Increases cartilage stiffness
What pathological change occurs in cartilage in OA?
Distribution of collagen fibres decreases the strength of the solid matrix increasing permeability leading to joint effusions
What can cartilage thinning mean for a joint?
Predisposes to degenerative joint disease
What is junk accumulation?
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
What are the consequences of junk accumulation?
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
What are the systems theories of aging?
Neuroendocrine and immunologic
What are the cellular theories of ageing?
Free radicals or senscence/apoptosis/wear and tear
What are the molecular theories of ageing?
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
What are the evolutionary theories of ageing?
Antagonistic pleiotropy
Mutation accumulation
Disposable somatheory - natural selection means resources are invested in maintaining repair mechanisms until the organism has reproduced
What ageing changes occur in osteoarthritis?
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
What is joint congruency?
Articular cartilage thickness is inversely related to the congruence of the joint surfaces which equalises the stress in congruent and incongruent joints
What is a congruent joint?
Small thickness of cartilage deforms a small amount but surface area is sufficiently large to distribute load
What is an incongruent joint?
Large thickness of cartilage depresses so that the surface area under compression is sufficient to decrease the stress appropriately