The Unknown Prevalence of Postrandomization Bias in 15 Physical Therapy Journals: A Methods Review

Document Type

Peer-Reviewed Article

Publication Date



Objectives: To determine the prevalence of prospective clinical trial registration and post-randomization bias in published musculoskeletal physiotherapy/physical therapy randomized clinical trials (RCTs).

Design: A methods review.

Literature search: Articles indexed in MEDLINE and published between January 2016 and July 2020 were included.

Study selection criteria: Two independent, blinded reviewers identified the RCTs using Covidence. We included RCTs related to musculoskeletal interventions that were published in International Society of Physiotherapy Journal Editors (ISPJE) member journals.

Data synthesis: Data were extracted for the variables of interest from the identified RCTs by two blinded reviewers independently. The data were presented descriptively or in frequency tables.

Results: One hundred and thirty-eight RCTs were identified. One-third of RCTs were consistent with their prospectively-registered intent (49/138); Consistency with prospectively intent could not be determined for two-thirds (89/138) of the RCTs. Four RCTs (3%) reported inconsistent results with the primary aims and outcomes from the prospective clinical trial registry despite high methodological quality (PEDro score). Differences between registered and unregistered RCTs for PEDro scores had a medium effect size (r=0.30). Two of 15 journals followed their clinical trial registration policy 100% of the time; in one journal, the published RCTs were consistent with the clinical trial registration.

Conclusion: Post-randomization bias in musculoskeletal physiotherapy/physical therapy RCTs could not be ruled out due to the lack of prospective clinical trial registration and detailed data analysis plans.


Online ahead of print 21 September 2021.






Journal of Orthopaedic & Sports Physical Therapy