Background: Hand osteoarthritis is a disabling condition with few effective therapies. Hand osteoarthritis with synovitis is a common inflammatory phenotype associated with pain. We aimed to examine the efficacy and safety of methotrexate at 6 months in participants with hand osteoarthritis and synovitis.

Methods: In this multisite, parallel-group, double-blind, randomised, placebo-controlled trial, participants (aged 40-75 years) with hand osteoarthritis (Kellgren and Lawrence grade ≥2 in at least one joint) and MRI-detected synovitis of grade 1 or more were recruited from the community in Melbourne, Hobart, Adelaide, and Perth, Australia. Participants were randomly assigned (1:1) using block randomisation, stratified by study site and self-reported sex, to receive methotrexate 20 mg or identical placebo orally once weekly for 6 months. The primary outcome was pain reduction (measured with a 100 mm visual analogue scale; VAS) in the study hand at 6 months assessed in the intention-to-treat population. Safety outcomes were assessed in all randomly assigned participants. This trial was registered with the Australian New Zealand Clinical Trials Registry (ACTRN12617000877381).

Findings: Between Nov 22, 2017, and Nov 8, 2021, of 202 participants who were assessed for eligibility, 97 (48%) were randomly assigned to receive methotrexate (n=50) or placebo (n=47). 68 (70%) of 97 participants were female and 29 (30%) were male. 42 (84%) of 50 participants in the methotrexate group and 40 (85%) of 47 in the placebo group provided primary outcome data. The mean change in VAS pain at 6 months was -15·2 mm (SD 24·0) in the methotrexate group and -7·7 mm (25·3) in the placebo group, with a mean between-group difference of -9·9 (95% CI -19·3 to -0·6; p=0·037) and an effect size (standardised mean difference) of 0·45 (0·03 to 0·87). Adverse events occurred in 31 (62%) of 50 participants in the methotrexate group and 28 (60%) of 47 participants in the placebo group.

Interpretation: Treatment of hand osteoarthritis and synovitis with 20 mg methotrexate for 6 months had a moderate but potentially clinically meaningful effect on reducing pain, providing proof of concept that methotrexate might have a role in the management of hand osteoarthritis with an inflammatory phenotype.

Funding: National Health and Medical Research Council of Australia.