Objectives: To evaluate whether elderly people and women are adequately represented in randomized controlled trials (RCT) in rheumatoid arthritis (RA) and osteoarthritis (OA). Methods: Four systematic searches in MEDLINE yielded RCT in RA and OA on any intervention published in 2016 and 2017 and population-based studies (PBS) in RA and OA published between 2013 and 2017. Random effects meta-analyses estimated the pooled proportion of elderly people (defined as being ≥ 65 years old), the mean age, its standard deviation (SD), and the proportion of women stratified by disease (RA and OA) and study type (RCT and PBS). Stratified estimates were subsequently compared. Results: 265 RCT comprising 51,240 participants and 53 PBS comprising 523,630 participants were included. In both RA and OA, RCT included lower proportions of elderly people than PBS: RA –0.18 (95% confidence interval –0.22 to –0.13); OA –0.20 (–0.30 to –0.09); had lower mean ages: RA –5.2 years (–6.8 to –3.5); OA –4.7 years (–7.5 to –2.0); and smaller SD: RA –1.9 years (–2.6 to –1.3); OA –2.7 years (–4.2 to –1.2); (all comparisons: p ≤ 0.001). Proportions of women were comparable in RCT compared to PBS in both RA and OA. Conclusions: While women are adequately represented in RA and OA trials, the elderly are underrepresented, probably limiting applicability of current evidence to this growing subgroup. It is urgent to improve the inclusion of elderly people in clinical trials and study age as a determinant for outcome.