Systematic review of cost-effectiveness analyses of weight loss interventions for knee osteoarthritis.

OBJECTIVES: We evaluated the cost-effectiveness of weight-loss interventions for adults with knee osteoarthritis (OA) and obesity. DESIGN: Systematic review and narrative synthesis. DATA SOURCES: MEDLINE, EMBASE via Ovid, Global Index Medicus and Web of Science and a clinical trial registry (ClinicalTrials.gov), published up to June 2025. ELIGIBILITY CRITERIA: English-language studies evaluating the cost-effectiveness of intentional weight-loss interventions in adults (≥18 years) with knee OA were included. Studies without cost-effectiveness outcomes, abstracts and conference proceedings were excluded. DATA EXTRACTION AND SYNTHESIS: Two reviewers independently extracted study characteristics and economic outcomes. A narrative synthesis was conducted and costs were standardised to 2024 British pounds. RESULTS: 1014 references were identified; eight studies met inclusion criteria, including six model-based economic evaluations and two randomised trials. Most studies used lifetime horizons and presented data from healthcare or societal perspectives. Combined diet and exercise programmes showed quality-adjusted life years (QALY) gains of 0.05-0.16 with incremental cost-effectiveness ratios (ICERs) of £16 915 and £31 305 per QALY, while bariatric surgery yielded larger gains (0.81-1.7 QALYs) at lower ICERs (£4361 to £19 303 per QALY). Pharmacological interventions were effective but costly with ICER (£32 265 to £35 832 per QALY). Evidence regarding telehealth-only interventions was mixed, with reported ICERs ranging from no significant effect to £32 722 per QALY gained. The included studies fulfilled 79-86% of the criteria from Consolidated Health Economic Evaluation Reporting Standards (CHEERS) checklist and were all rated good on the Drummond checklist. CONCLUSIONS: Using standard UK cost-effectiveness thresholds (£25 000 to £35 000 per QALY), bariatric surgery appears most likely to be cost-effective for patients with knee OA, although this conclusion is based primarily on US model-based evidence. Pharmacological therapies may be cost-effective, although their economic value is sensitive to drug pricing and willingness-to-pay thresholds. High-quality UK-based economic evaluations are needed to establish the cost-effectiveness of Glucagon-Like Peptide-1 (GLP-1) receptor agonists for knee OA.