Osteoarthritis Flashcards
osteoarthritis
progressive degenerative changes in the shape, composition, and mechanical properties of joint tissues, especially the articular cartilage, leading to joint malfunction
most common form of arthritis?
OA (75% of people)
components of articular cartilage
matrix and chondrocytes
composition of matrix
60-80% water.
Dry weight: 2/3 type 2 collagen and 1/3 proteoglycan
collagen in matrix
type 2, provides tensile strength
proteoglycan in matrix
negative charge, resists compression
what happens when force is applied to a joint?
cartilage compresses and water is squeezed out. shock is absorbed. water then returns via the negative charges of the proteoglycans and cartilage reforms
what is cartilage matrix lacking?
blood vessels and nerves.
what lies between bone and cartilage in joint?
calcified cartilage
synovium
2-3 cells thick, synoviocytes/blood vessels/lymphatics/nerves in posse bed of connective tissue
synovial fluid
provides nutrition to chondrocytes, helps remove waste, primary role is lubrication via lubricin and hyaluronic acid
main characteristic of OA
loss of cartilage and consequential functional abnormality
inflammation in OA
chronic, low grade inflammation that is not a driver of the disease but aids in progress. synoviocytes release cytokines that activate proteases that chomp away at cartilage
mechanical factors of OA
macrotrauma, microtrauma+time
biochemical factors of OA
inflammation, proteases, imperfect repair
who is more affected by OA
women!
clinical manifestations of OA
decreased ROM, contractures, crepitus, osteophytes
heberden’s node
osteophytes presenting on DIP
bouchard’s node
osteophytes presenting on PIP
what happens when there is abnormal loading on a joint?
decreased proteoglycan synthesis
macroscopic changes indicative of OA
eburnation, fibrillations, cartilage thinning
microscopic changes indicative of OA
clefts at surface, clustering of chrondrocyte clones, fewer chondrocytes overall
composition changes indicative of OA
decreased: type 2 collagen, proteoglycans
increased: type 1 collagen, water content, glycated proteins (all leading to decreased stiffness and softening)
why is cartilage poor at repair?
poor vascular supply, chondrocytes are immobile
sclerosis
increase in bone density. in OA, commonly occurs at the subchondral bone
early stage OA bone changes
subchondral bone thins because resorption outpaces formation
late stage OA bone changes
calcified cartilage thickens, subchondral bone thickens (but is poorly mineralized and brittle), trabecular bone thins
synovium pathology in OA
hyperplasia, macrophage/lymphocyte infiltrates, fibrosis, neoangiogenesis (VEGF)
synovial fluid changes in OA
decreased concentrate of lubricants, decreased concentration and molecular weight of hyaluronic acid
OA and obesity
8x risk, increased load and inflammation lead to OA in joints everywhere, weight loss improves symptoms
