Objective. To assess the methodological quality of randomized controlled trials (RCT) of medical and surgical therapy in patients with arthroplasty. Methods. We conducted a Medline database search for all arthroplasty RCT from 1997 and 2006. The quality of the methods of all eligible RCT was assessed by a trained abstractor.We used a checklist of trial quality characteristics, and the overall trial quality was assessed by 3 scales: Jadad (range 0-5), Delphi list (range 0-9), and numeric rating scale (NRS; range 1-10), based on User's Guides to the Medical Literature. Results. A total of 196 articles were included in the analysis; most included hip (n = 81) or knee (n = 80) or both hip/knee arthroplasty (n = 19); 66 (34%) assessed pharmacological treatments, 117 (60%) nonpharmacological treatments, and 13 (7%) both. Mean (SEM) overall quality scores of arthroplasty RCT were low: Jadad score 2.36 (1.4), Delphi list 5.33 (1.6), and NRS score 4.30 (2.6). Multivariable analyses revealed that nonpharmacological intervention RCT had lower odds (odds ratio 0.28-0.39; p = 0.008-0.033) and those with no funding had lower odds (OR 0.28-0.50; p = 0.014-0.119) of being in the highest quartiles of the 3 overall quality scores. In contrast, multicenter RCT had 1.8-4.7 times higher odds of being in highest tertiles of quality scores (p = 0.017-0.185). Conclusion. Methodological deficiencies in reporting of hip/knee arthroplasty RCT offer an opportunity for improvement. Type of intervention, number of trial centers, and presence of funding were independently associated with overall trial quality. In future, multicenter RCT (rather than single-center) and modeling protocols of single-center RCT similar in rigor to multicenter RCT may improve the quality of arthroplasty RCT. The Journal of Rheumatology Copyright © 2009. All rights reserved.