5.2: Cartilage biology and osteoarthritis

Question 1

Osteoarthritis is a disease of

Answer 1

The whole joint which involves the loss of articular cartilage

Question 2

Healthy cartilage is composed of what three things

Answer 2

Proteoglycan
Type 2 collagen
Water

Question 3

What is the function of Proteoglycan in cartilage

Answer 3

Exert swelling pressure, resists compression

Question 4

Function of type 2 collagen in cartilage

Answer 4

Exerts high tensile strength

Question 5

Characteristics of the chondrocyte

Answer 5

Producer and degraded of cartilage matrix
Highly metabolically active
Exists in relative hypoxia
Interactions with matrix : growth factors, mechano-transduction
No cell division after adolescence

Question 6

Intrinsic anabolic and anti-catabolic factors for articular cartilage in the joint

Answer 6

TIMPs -Tissue Inhibitor of Metalloproteinases (1-4)
Growth factors e.g fibroblast growth factor (FGF-2), Insulin-like growth factor, transforming growth factor, activin A

Question 7

Extrinsic anabolic and anti-catabolic factors for articular cartilage in the joint

Answer 7

Hormones e.g. testosterone, estrogen
Some drugs e.g FGF-18

Question 8

Why does matrix loss occur

Answer 8

Imbalance in Excessive degradation and reduced anabolism/repair

Question 9

3 processes in driving processes of osteoarthritis

Answer 9

Inflammation
Pain
Repair remodelling

Question 10

Molecular changes during osteoarthritis onset

Answer 10

Excessive fragmentation of Proteoglycan into synovial fluid
Cartilage fragmented by collaginases
Loss of matrix resulting in inflammation

Question 11

7 Risk factors for OA development

Answer 11

Age
Obesity
Mechanical factors
Family history
Chondrodysplasis
Other medical conditions e.g haemochromatosis
Secondary joint damage due to inflammatory arthropathies

Question 12

Evidence for mechanical factors increasing OA (4)

Answer 12

Destabilising joint injuries increase risk of OA
Intra-articular fracture increase risk
Occupational examples - “coal miners back”
Mal-aligned joints get OA

Question 13

What joints are usually protected from OA

Answer 13

Paralysed joints

Question 14

Cartilage loss after injury is what kind of process and what does it depend on

Answer 14

Active biological process depending on an aggrecanase

Question 15

Why is osteoarthritis increasing?

Answer 15

Older worldwide population
Increasing rates of obesity

Question 16

How is osteoarthritis diagnosed?

Answer 16

Clinical diagnosis:
Joint pain typically on activity
Stiffness typical <30min
Loss of function
Examination findings: bony deformity at joint line

X-ray
Blood tests

Question 17

Blood test results used to diagnose osteoarthritis

Answer 17

Normal CRP
Rheumatoid arthritis tests are negative
Other tests can be relevant to exclude secondary causes

Question 18

Surgical options for OA

Answer 18

Total joint replacement - arthroplasty -hip or knee
Uni-compartmental replacement for knee possible
Trapeziectomy - removal of thumb bone

Question 19

Matrix catabolism results from

Answer 19

Signalling downstream of mechanical injury

Question 20

New treatments for OA

Answer 20

Treating pain
Improving function

Question 21

Post traumatic OA is

Answer 21

Arthritis that occurs post injury - inflammatory response in joint injury in response to trauma