The optimal methods of determining outcomes following hip and knee arthroplasty remain controversial. The objectives of this study were to determine the most frequently used outcome measures in randomized controlled trials (RCT) and study protocols registered with clinical trials registries (CTR) on hip and knee arthroplasty.A systematic search strategy was undertaken to identify the outcome measures used in RCT and CTR following joint arthroplasty. Databases searched included Embase, Ovid MEDLINE (including In-Process), Cochrane Central Register of Controlled Trials, CINAHL Plus, clinicaltrials.gov, ISRCTN registry, and ANZCTR. Differences in the use of outcome measures between RCT and CTR were assessed using logistic regression.There were 291 RCT and 113 CTR on hip arthroplasty and 452 RCT and 184 CTR on knee arthroplasty that met the inclusion criteria. The most popular outcome measures were the Harris Hip Score and the Knee Society Score. Multiple outcome measures were used in greater than 50% of the included studies. The Oxford Hip Score, Oxford Knee Score, EuroQol-5D, and Knee Injury and Osteoarthritis Outcome Score (all P < .001) were used in significantly more CTR than RCT.There is a clear preference for the use of the Harris Hip Score and Knee Society Score, contrary to existing international guidelines and reviews on the topic. Both measures require clinician input, which potentially influences their validity and increases their overall administration cost. Some patient-reported outcome measures, such as the Oxford Hip and Knee Scores, EuroQol-5D, and KOOS, appear to be increasing in popularity.