5.2: Cartilage biology and osteoarthritis Flashcards
Osteoarthritis is a disease of
The whole joint which involves the loss of articular cartilage
Healthy cartilage is composed of what three things
Proteoglycan
Type 2 collagen
Water
What is the function of Proteoglycan in cartilage
Exert swelling pressure, resists compression
Function of type 2 collagen in cartilage
Exerts high tensile strength
Characteristics of the chondrocyte
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
Intrinsic anabolic and anti-catabolic factors for articular cartilage in the joint
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
Extrinsic anabolic and anti-catabolic factors for articular cartilage in the joint
Hormones e.g. testosterone, estrogen
Some drugs e.g FGF-18
Why does matrix loss occur
Imbalance in Excessive degradation and reduced anabolism/repair
3 processes in driving processes of osteoarthritis
Inflammation
Pain
Repair remodelling
Molecular changes during osteoarthritis onset
Excessive fragmentation of Proteoglycan into synovial fluid
Cartilage fragmented by collaginases
Loss of matrix resulting in inflammation
7 Risk factors for OA development
Age
Obesity
Mechanical factors
Family history
Chondrodysplasis
Other medical conditions e.g haemochromatosis
Secondary joint damage due to inflammatory arthropathies
Evidence for mechanical factors increasing OA (4)
Destabilising joint injuries increase risk of OA
Intra-articular fracture increase risk
Occupational examples - “coal miners back”
Mal-aligned joints get OA
What joints are usually protected from OA
Paralysed joints
Cartilage loss after injury is what kind of process and what does it depend on
Active biological process depending on an aggrecanase
Why is osteoarthritis increasing?
Older worldwide population
Increasing rates of obesity
How is osteoarthritis diagnosed?
Clinical diagnosis:
Joint pain typically on activity
Stiffness typical <30min
Loss of function
Examination findings: bony deformity at joint line
X-ray
Blood tests
Blood test results used to diagnose osteoarthritis
Normal CRP
Rheumatoid arthritis tests are negative
Other tests can be relevant to exclude secondary causes
Surgical options for OA
Total joint replacement - arthroplasty -hip or knee
Uni-compartmental replacement for knee possible
Trapeziectomy - removal of thumb bone
Matrix catabolism results from
Signalling downstream of mechanical injury
New treatments for OA
Treating pain
Improving function
Post traumatic OA is
Arthritis that occurs post injury - inflammatory response in joint injury in response to trauma