Osteoarthritis (OA) is a degenerative joint disease for which there are no disease-modifying drugs. It is a leading cause of disability in the UK. Increasing age and obesity are both major risk factors for OA and the health and economic burden of this disease will increase in the future. Focusing on compounds from the habitual diet that may prevent the onset or slow the progression of OA is a strategy that has been under-investigated to date. An approach that relies on dietary modification is clearly attractive in terms of risk/benefit and more likely to be implementable at the population level. However, before undertaking a full clinical trial to examine potential efficacy, detailed molecular studies are required in order to optimise the design. This review focuses on potential dietary factors that may reduce the risk or progression of OA, including micronutrients, fatty acids, flavonoids and other phytochemicals. It therefore ignores data coming from classical inflammatory arthritides and nutraceuticals such as glucosamine and chondroitin. In conclusion, diet offers a route by which the health of the joint can be protected and OA incidence or progression decreased. In a chronic disease, with risk factors increasing in the population and with no pharmaceutical cure, an understanding of this will be crucial.Osteoarthritis: Diet: Cartilage: Bioactive: Polyphenol: Phytochemical: Flavonoid Osteoarthritis (OA) is a degenerative joint disease characterised by degradation of articular cartilage, thickening of subchondral bone and osteophyte formation. Incidence and prevalence of OA has been difficult to assess, in part because of heterogeneity in definitions of the disease. A recent meta-analysis suggested that overall prevalence of OA at different anatomical sites was 23·9 % (knee), 10·9 % (hip) and 43·3 % (hand), although only the prevalence of knee OA showed a gender difference between women and men (27·3 and 21 %, respectively)(1) . Osteoarthritis is a leading cause of disability in the UK. A recent survey (2) found 8·5 million people in the UK with OA, with 71 % of these in constant pain. There are no effective disease-modifying drugs to treat OA and drugs that relieve pain are often insufficient. Joint replacement is offered to patients at end-stage disease with 66 436 hip and 77 578 knee replacements due to OA performed in the UK in 2011 (3) . Two major risk factors for OA are increasing age (most affected patients are aged >45 years and the greatest morbidity is seen in patients aged >60 years) (4) and increasing obesity (5) . With changing demographics, OA is an increasing public health and economic burden. The economic costs of OA in the UK are largely unknown, but direct costs have been estimated at approximately £1 billion/year. With inclusion of indirect costs, estimates from the USA range up to £8 billion/ year (6) .*Corresponding author: I. M. Clark, fax 01603-592250, email i.clark@uea.ac.uk †These authors contributed equally to this review.Abbreviations: ADAMTS, a disintegrin and metalloproteina...