This systematic review assessed the cost-effectiveness of intentional weight-loss interventions for adults (≥18 years) with knee osteoarthritis (OA) and obesity. The authors aimed to identify and synthesise economic evaluations that report cost-effectiveness outcomes for diet, exercise, pharmacological, surgical and telehealth weight-loss strategies in this patient group. The review included studies published up to June 2025.
Searches were conducted across MEDLINE, EMBASE via Ovid, Global Index Medicus, Web of Science and the clinical trial registry ClinicalTrials.gov. Only English-language studies that evaluated cost-effectiveness outcomes for intentional weight-loss interventions in adults with knee OA were eligible. Abstracts and conference proceedings without full economic outcomes were excluded.
Two reviewers independently extracted study characteristics and economic outcomes. A narrative synthesis was performed rather than meta-analysis. Reported costs were standardised to 2024 British pounds for comparison across studies.
From 1,014 references identified, eight studies met inclusion criteria. The included evidence comprised six model-based economic evaluations and two randomised trials that reported cost-effectiveness outcomes. Most studies adopted lifetime horizons and presented analyses from healthcare and/or societal perspectives.
Diet and exercise programmes
Combined diet-and-exercise programmes reported modest gains in quality-adjusted life years (QALYs) of 0.05 to 0.16. Incremental cost-effectiveness ratios (ICERs) in these studies were reported at £16,915 and £31,305 per QALY.
Bariatric surgery
Bariatric surgery interventions produced larger QALY gains, reported between 0.81 and 1.7 QALYs. Reported ICERs for bariatric procedures ranged from £4,361 to £19,303 per QALY. Within the studies synthesised, bariatric surgery consistently showed more favourable cost-effectiveness metrics compared with non-surgical strategies.
Pharmacological interventions
Pharmacological weight-loss therapies were effective in health outcome terms but incurred higher costs. Reported ICERs for drug interventions ranged from £32,265 to £35,832 per QALY. The economic attractiveness of pharmacological options was noted to be sensitive to drug pricing and to the selected willingness-to-pay threshold.
Telehealth-only interventions
Evidence for telehealth-only weight-loss interventions was mixed. Some studies reported no significant cost-effectiveness advantage, while others reported ICERs up to £32,722 per QALY gained.
Comparative context against UK thresholds
When mapped to standard UK cost-effectiveness thresholds (£25,000 to £35,000 per QALY), bariatric surgery appeared most likely to be cost-effective based on the included data. Diet-and-exercise programmes fell within or below these thresholds in some models, while pharmacological and telehealth interventions were variably within or above thresholds depending on price assumptions and model inputs.
The included studies fulfilled between 79% and 86% of the items on the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) checklist. All studies were rated as good using the Drummond checklist for economic evaluations. These assessments indicate generally acceptable reporting and methodological quality across the identified literature, though heterogeneity exists in model structures, time horizons and perspective choices.
Applying the conventional UK willingness-to-pay range (£25,000 to £35,000 per QALY), the review found that bariatric surgery is most likely to meet cost-effectiveness criteria for patients with knee OA and obesity. However, the authors note this conclusion is primarily supported by US model-based evidence rather than UK-specific analyses.
Pharmacological therapies, including contemporary agents referenced as relevant to obesity management, may be cost-effective only if drug prices and pricing policies align with willingness-to-pay thresholds. The review highlights that the economic value of pharmacotherapies is particularly sensitive to price assumptions.
Bariatric surgery appears most likely to be cost-effective for obese adults with knee OA when assessed against UK thresholds, based largely on available model-based evidence. Pharmacological options may approach or meet cost-effectiveness thresholds but their status depends on drug pricing and threshold decisions. The review identifies a need for high-quality, UK-based economic evaluations, specifically to establish the cost-effectiveness of Glucagon-Like Peptide-1 (GLP-1) receptor agonists for knee OA. Details regarding subgroup effects, long-term real-world effectiveness and country-specific cost structures were not fully addressed in the included studies and were noted as gaps for future research.