To develop and validate a questionnaire assessing patient knowledge in rheumatoid arthritis (RA). Knowledge considered essential for patients with RA was identified through a series of Delphi rounds among rheumatologists, health professionals (HPs), patients, and then reformulated to construct the knowledge questionnaire. Cross-sectional multicenter validation was performed in 12 rheumatology departments to assess internal validity (Kuder\textendash Richardson coefficient), external validity, acceptability, reproducibility (Lin's concordance correlation coefficient) and sensitivity to change (difference in total score before and after patient education sessions). Associations between patient variables and knowledge levels were evaluated. RAKE (RA Knowledge questionnairE) is a self-administered 45-item questionnaire scored 0\textendash 100, with a 32-item short-form survey assessing knowledge of disease, comorbidity, pharmacological treatments, non-pharmacological treatments, self-care and adaptative skills. Of 130 patients included in the validation study, 108 were women. Acceptability was good with\,<\,5% missing data. Internal validity coefficient was 0.90. Mean (standard deviation) long-form score was 72.8\,±\,17.8, with lower scores in comorbidity and self-care and higher scores in adaptive skills. Reproducibility was good (0.86 [0.80; 0.92]). RAKE score was positively correlated with the patients' level of education and the HPs' opinion on the patients' knowledge. RAKE score showed good sensitivity to change: 66.8\,±\,16.4 then 83.8\,±\,12.7, representing a hedges effect size of 1.14 [95% CI 0.73; 1.55]. RAKE is an updated questionnaire assessing essential knowledge for patients with RA to enhance self-management according to current guidelines and the patients' perspective. RAKE can usefully inform patient education interventions, routine care and research.