Osteoarthritis Flashcards
What is the definition of osteoarthritis (NICE, 2022)
Disorder of synovial joints which occurs when damage triggers repair processes leading to structural changes within a joint
How does damage occur to the joint in OA
Repetitive excessive loading / stress of joint
Injury
What are the affected joints in OA
Any synovial joint
especially affects knees (18%), hips (8%) and hand and wrist (6%)
Often bilateral
What aspects of synovial joints are often affected in OA?
Structural alterations include:
hyaline articular cartilage
subchondral bone
ligaments
capsule
synovium
periarticular muscles
What is the epidemiology for OA
Most common joint disease
15% of world population worldwide
Women > men
1/3 women and 1/4 men sought treatment (45-64yrs)
1/2 75yrs+ sought treatment
What are the causes and affected areas of primary OA
Can be genetic, biological and biomechanical
Occurs in older age
no apparent underlying reason
mostly weight-bearing joints
can also affect 1st CMC and distal IP joints
What are the causes and affected areas for secondary OA
Genetic, biological and biomechanical aspects
Consequence of abnormal force across joint
e.g. post-trauma, deformity
Abnormal articular cartilage
e.g. disease, infection
What are risk factors for OA
Age
Obesity
genetics
heavy work (construction, farming, kneeling, lifting)
High impact sports
Trauma / injury
Hip deformities or dysplasia
Knee malignment
what is the pathophysiology of OA
Pathophysiology
- Normal articular cartilage = extracellular matrix (water, collagen, proteoglycans + calcium salt) and chondrocytes
- Dynamic remodelling process - normal turnover of matrix constituents is mediated by chondrocytes, which synthesise the components + proteolytic enzymes responsible for their breakdown.
- OA results from failure of the chondrocytes to maintain homeostasis between synthesis and degradation of extracellular matrix constituents
- Unclear what initiates this imbalance between degradation + repair of cartilage
- Matrix degrading enzymes are overexpressed, shifting the balance towards degradation, resulting in loss of collagen and proteoglycans from matrix
- Initially chondrocytes proliferate in response to the loss, synthesising more proteoglycan and collagen molecules, but over time reparative attempts are surpassed by progressive cartilage degeneration
what is the cycle of biomechanical and biochemical degradation (simple)
Repair mechanisms -> remodelling within cartilage within cartilage and subchondral bone -> damage to repair -> degeneration of cartilage and bone -> load disruption affected
What are possible changes to articular cartilage due to OA
Softening
fibrillation
fissuring
Reduced thickness
Erosion
Exposure of subchondral bone
What changes occur to the subchondral bone with OA
Exposure of underlying subchondral bone leading to sclerosis
Reactive remodelling of bone leads to formation of osteophytes at joint margine
Subchondral bone volume increases leading to joint space narrowing
development of bone marrow lesions and subchondral bone cysts
What general changes occur due to OA
Inflammation of the synovium and surrounding capsule
Increased synovial fluid
Joint capsule and ligaments may thicken to try to stabilise the joint as it changes shape
How is OA diagnosed
Based on symptoms and physical examination (imaging not required for diagnosis)
What are symptoms of OA
Pain
Brief morning stiffness
functional limitations
