ObjectiveThe aim was to evaluate the cost-utility of a 3-month multimodal occupational therapy intervention in addition to usual care in patients with thumb carpometacarpal osteoarthritis (CMC1 OA).MethodsA cost-utility analysis was performed alongside a multicentre randomised controlled trial including three rheumatology departments in Norway. A total of 180 patients referred to surgical consultation due to CMC1 OA were randomised to either multimodal occupational therapy including patient education, hand exercises, assistive devices and orthoses (n=90), or usual care receiving only information on OA (n=90). The outcome measure was quality-adjusted life-years (QALYs) derived from the generic questionnaire EQ-5D-5L over a 2-year period. Resource use and health-related quality of life of the patients were prospectively collected at baseline, 4, 18 and 24 months. Costs were estimated by taking a healthcare and societal perspective. The results were expressed as incremental cost-effectiveness ratios, and a probabilistic sensitivity analysis with 1000 replications following intention-to-treat principle was done to account for uncertainty in the analysis.ResultsDuring the 2-year follow-up period, patients receiving multimodal occupational therapy gained 0.06 more QALYs than patients receiving usual care. The mean (SD) direct costs were €3227 (3546) in the intervention group and €4378 (5487) in the usual care group, mean difference €−1151 (95% CI −2564, 262). The intervention was the dominant treatment with a probability of 94.5% being cost-effective given the willingness-to-pay threshold of €27 500.ConclusionsThe within-trial analysis demonstrated that the multimodal occupational therapy in addition to usual care was cost-effective at 2 years in patients with CMC1 OA.Trial registration numberNCT01794754.