Osteoarthritis

Question 1

what are the risk factors of osteoarthritis?

Answer 1

1. age
   - 25% >50yes have knee OA
2. women
3. obesity
4. smoking
5. hypermobility
6. osteoporosis

Question 2

what is OA?

Answer 2

Question 3

what does articular cartilage do? where is it?

Answer 3

absorb load of the joint
- knee joint - end of femur and tibia
- hip joint - fem

Question 4

what is the structure of articular cartilage?

Answer 4

made up of chrondrocytes
produce proteins that form the extracellular matrix

Question 5

what are proteins that form the extracellular matrix?

Answer 5

1. Network of Type II Collagen fibres
2. Proteoglycans containing glycosaminoglycan (GAG) side- chains
   * “Bottle-brush” appearance
   * Trap water, which provides cartilage with its load absorbing properties
3. Non-collagenous proteins including fibronectin

Question 6

how does articular cartilage absorb load?

Answer 6

When load is applied to the joint cartilage compresses H2O
In turn repulsive forces from proteoglycans within the extracellular matrix balance the load applied
On removing load, proteoglycans rehydrate restoring shape of cartilage

Question 7

what is chondrocyte hypertrophy?

Answer 7

chondrocyte proliferate and undergo hypertrophy :
1. induce transcriptional factors = increase hypertrophy
2. reduce matrix synthesis - collagen and aggrecan proteoglycan
3. increase matrix proteases

Question 8

how does cartilage degeneration occur in OA?

Answer 8

catabolic processes:
1. matrix metalloproteases (MMPs) - degrade type 2 collagen
2. aggrecanases - degrade aggrecan proteoglycans

Question 9

how is the subchondral bone describes in OA?

Answer 9

sclerotic

Question 10

how is bone described in OA?

Answer 10

undermineralised
abnormal type 1 collage - increase expression of alpha-1 collagen = kink structure = brittle bone

Question 11

what does OA synovitis cause?

Answer 11

inappropriate activity of fibroblast cells = increase joint damage and joint pain

Question 12

whats first line for OA treatment?

Answer 12

1. topical/oral NSAID’s
   - aspirin/ibuprofen (long-term GI issues)

OR
selective COX-2 inhibitors for long term use - less GI issues but INC CV risk
- celecoxib/meloxicam

2. GC intra-articular injection used in knee OA
   - known to also accelerate cartilage damage

Question 13

how do GC accelerate cartilage damage?

Answer 13

1. increase RANKL = decrease OPG secretion from osteoblasts
2. chronic increase of PTH and reduction in BMP2 = decreases osteoblasts proliferation
3. increase apoptosis of osteocytes = decrease load sensing and initiation of bone remodelling

Question 14

why is obesity a risk factor for OA?

Answer 14

1. traumatic loading can induce cartilage damage= increasing cartilage fragmentation
2. increased adipose tissue secrete cytokines (pr-inflammatory)

Question 15

what does a high WHR suggest?

Answer 15

metabolic syndrome related effect