**Background:** Osteoarthritis is a chronic degenerative joint disease and the most common form of arthritis leading to knee and hip replacements in Australia, affecting an estimated 9.3% of the total population. Prevalence increases markedly with age, rising from 9.7% in those aged 45–54 years to 20.7% in those aged 55–64 years, and affects approximately 6% of Australian males (n = 805,800 estimated) and 10% of Australian females (n = 749,200 estimated). While low intake of nutrients such as vitamin D, C, E, K, and magnesium has been associated with increased osteoarthritis risk, randomised controlled trials supplementing single nutrients have not shown protective effects, suggesting that whole dietary patterns and food groups should be the focus of diet–disease research. This systematic review aimed to scope associations between dietary patterns, diet quality, and food groups with symptomatic osteoarthritis (defined as joint pain, aching, or stiffness plus radiographic osteoarthritis) in adults aged 45 years and older.
**Methods:** The review was registered on PROSPERO (CRD42021270891) and reported following PRISMA guidelines. A comprehensive literature search was conducted on 2 September 2021 across Cochrane CENTRAL Library (via Ovid), CINAHL, Embase (via Ovid), MEDLINE (via Ovid), and Web of Science. Reference lists of included articles were searched by 4 October 2021. A total of 3816 records were identified; after removing 804 duplicates, 3012 papers were screened by title and abstract, and 48 articles were retrieved for full-text assessment. Six cohort studies ultimately met the inclusion criteria. Eligible studies involved populations aged ≥45 years with symptomatic osteoarthritis, assessed dietary patterns, diet quality, or food groups, and measured joint pain, stiffness, or physical function as outcomes. Quality assessment was performed using the Joanna Briggs Institute Critical Appraisal Checklists, and the certainty of evidence was evaluated using the GRADE approach. Data extraction and quality assessment were conducted in duplicate by two reviewers.
**Key Results:** All six included articles were prospective cohort studies: four from the United States (Osteoarthritis Initiative), one from Australia (VIDEO study), and one comparing the Osteoarthritis Initiative and Framingham Offspring cohorts. Sample sizes ranged from 392 to 4470 participants, with follow-up periods from 2 to 9.5 years. The Prudent dietary pattern significantly reduced symptomatic osteoarthritis progression (highest vs lowest quartile: OR 0.71 [95% CI 0.60, 0.84], p-trend <0.01). The Western dietary pattern significantly increased symptomatic osteoarthritis progression (highest vs lowest quartile: OR 1.26 [95% CI 1.06, 1.50], p-trend <0.01). Greater adherence to the Mediterranean diet reduced pain worsening (aMED score >32: RR 0.96 [95% CI 0.91, 0.999], p = 0.047) and incident symptomatic knee osteoarthritis (aMED >32: RR 0.91 [95% CI 0.82, 0.998], p = 0.048), though overall trends were inconclusive. A higher dietary inflammatory potential was associated with increased risk of symptomatic knee osteoarthritis (highest vs lowest quartile of Energy-adjusted Dietary Inflammatory Index: OR 1.43 [95% CI 1.16, 1.76], p = 0.001). Higher total dietary fibre intake was inversely associated with pain worsening in the Osteoarthritis Initiative (highest vs lowest quartile: OR 0.85 [95% CI 0.74, 0.99], p-trend = 0.03) and with moderate and severe knee pain (moderate pain: OR 0.57 [95% CI 0.42, 0.77], p-trend = 0.0004; severe pain: OR 0.41 [95% CI 0.24, 0.68], p-trend = 0.0006). However, effects of fibre from individual food groups (cereal, fruit and vegetable, nut and legume) were largely inconclusive. Overall diet quality showed inconsistent results across two studies. The certainty of evidence assessed by GRADE was very low for symptomatic osteoarthritis progression, knee pain VAS, WOMAC joint stiffness, WOMAC knee pain, total WOMAC, WOMAC physical dysfunction, and WOMAC pain; it was low for pain worsening.
**Clinical Implications:** The Prudent dietary pattern demonstrated the strongest protective association against symptomatic osteoarthritis progression in adults aged 45 years and over, followed by the Mediterranean diet. These anti-inflammatory dietary patterns—characterised by high intakes of vegetables, fruits, fish, whole grains, and legumes—may reduce osteoarthritis symptoms through mechanisms involving lowered systemic inflammation, reduced oxidative stress, and beneficial effects on body weight. Conversely, Western and pro-inflammatory dietary patterns were associated with increased symptomatic osteoarthritis progression, likely mediated through inflammatory signalling and adipocyte dysfunction. The findings suggest that dietary modification could be a viable component of symptomatic osteoarthritis management, potentially informing future clinical guidelines. However, the body of evidence is limited by low to very low certainty due to the observational study designs, heterogeneity in dietary assessment methods and outcome definitions, risk of bias, and imprecision. Further research—particularly randomised controlled trials and cohort studies with consistent exposure and outcome measures—is needed to corroborate these estimated effects at a higher certainty of evidence and to investigate previously unstudied dietary patterns such as the DASH diet.