Introduction Hand osteoarthritis (HOA) is a highly prevalent disabling joint disease. The current management regimens are limited. Potentially as a consequence, many people turn to complementary and alternative medicines for symptomatic relief. A combination of two or more supplements is common in clinical practice; however, evidence for the efficacy of this approach is lacking. The aim of this study is to investigate the efficacy of a supplement combination for treating symptomatic HOA in comparison to placebo.

Methods and analysis The RADIANT study is an internet-based, parallel, superiority, double-blind, placebo-controlled, randomised, two-arm clinical trial. A participatory design is used to facilitate the study procedures. One hundred and six participants aged over 40 years with painful HOA and structural change on X-ray (Kellgren and Lawrence grade (KLG) ≥2) will be recruited from the community and randomly allocated to receive either a supplement combination composed of: (1) combined supplement containing Boswellia serrata extract, pine bark extract and methylsulfonylmethane and (2) curcumin or placebo for 12 weeks. The primary outcome will be 12-week change in hand pain on a visual analogue scale (VAS). Main secondary outcomes include adverse events, change in hand function, patient global assessment of disease activity and quality of life. A range of additional measures will be recorded, and an individual patient placebo response will be performed. The primary analysis will be conducted using an intention-to-treat approach. Adverse events will be monitored weekly throughout the study.

Ethics and dissemination This protocol has been approved by the University of Sydney Human Research Ethics Committee (HREC No. 2018/766). Dissemination will occur through conferences, social media, scientific publications and PhD thesis.

Trial registration number Australian New Zealand Clinical Trials Registry (ACTRN12619000835145); Pre-results