Many clinical trials are reported without reference to the existing relevant high-quality research. This is one source of waste in research. This study aimed to investigate the extent to which authors of articles reporting the primary results of clinical trials of physiotherapy interventions try to use high-quality clinical research to (1) help justify the need for the trial in the introduction section and (2) help interpret the trial’s results in the discussion section. Data were extracted from 221 clinical trials that were randomly selected from PEDro: 70 published in 2001 and 151 published in 2015. The total PEDro score for each trial was also downloaded. Overall, 41% of articles cited a systematic review or the results of a search for other evidence in the introduction section: 21% for 2001 and 50% for 2015 (relative risk 2.3, 95% confidence interval 1.5-3.8). For the discussion section, only 1 of 221 articles integrated the results of the trial into an existing meta-analysis, but citation of a relevant systematic review did occur in 29% of articles (increasing from 17% in 2001 to 34% in 2015). There was no relationship between citation of existing research and the total PEDro score. Articles reporting the primary results of clinical trials of physiotherapy interventions increasingly cite a systematic review or the results of a search for other evidence in the introduction section, but integration with existing research in the discussion section is very rare. To encourage the use of existing research, stronger recommendations to refer to existing systematic reviews (where available) could be incorporated into reporting checklists and journal editorial guidelines.