Osteoarthritis: epidemiology and pathophysiology of cartilage failure
How common osteoarthritis, osteoporosis and rheumatoid arthritis are in Australia, who gets OA and why, how cartilage, bone, synovium and meniscus fail together, where OA pain comes from, and the mechanics behind weight loss and the STEP 9 semaglutide trial.
Tier 1Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Osteoarthritis (OA) affects about 2.1 million Australians (8.3%), rising to about 30% of people 75 and over. It drives most of the roughly 53,500 knee and 35,500 hip replacements a year.
- OA is a whole-joint organ failure: cartilage, subchondral bone, synovium, meniscus, ligaments and muscle all change. It is not simple "wear and tear".
- The drivers are mechanical load on a joint, systemic factors (age, sex, obesity, genetics) and low-grade innate inflammation.
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Sources
- Chronic musculoskeletal conditions: osteoarthritis, rheumatoid arthritis and osteoporosisAU/NZAustralian Institute of Health and Welfare, 2024 (data from the 2022 ABS National Health Survey)
- Guideline for the management of knee and hip osteoarthritis (2nd ed.)AU/NZRoyal Australian College of General Practitioners, 2018
- OsteoarthritisLancet (Hunter and Bierma-Zeinstra, 2019;393:1745-1759), 2019
- Weight loss reduces knee-joint loads in overweight and obese older adults with knee osteoarthritisArthritis and Rheumatism (Messier et al., 2005;52:2026-2032), 2005
- Once-weekly semaglutide in persons with obesity and knee osteoarthritis (STEP 9)New England Journal of Medicine (Bliddal et al., 2024;391:1573-1583), 2024
- Kelley and Firestein's Textbook of Rheumatology (11th ed.)Elsevier (2021), 2021
- Last updated
- 14 November 2026
What changed
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