Registration and reporting characteristics of trials investigating exercise therapy following total knee arthroplasty: A systematic review.

ObjectivesProspectively registering the primary trial outcome is important to reduce selective outcome reporting and increase trustworthiness of findings used to guide clinical practice. The objective of this systematic review was to explore and compare the reporting characteristics of prospectively and non-prospectively registered trials investigating exercise therapy following total knee arthroplasty. DesignTrials comparing effects of exercise therapy after total knee arthroplasty due to osteoarthritis were sought in four databases from 2000 (clinicaltrials.gov launch) to 12th of August 2024. Randomised controlled trials comparing different exercise therapy interventions were included. Primary outcomes were extracted using a pre-specified hierarchy to reflect each trials most consistently reported outcome. Risk-of-bias was assessed using the Cochrane Collaborations Risk-of-Bias tool version 2. ResultsNinety-four trials (n = 9,396) were included: 13 prospectively registered, 33 retrospectively registered, and 48 unregistered. A single primary outcome was defined in 43.6% of trials. Four trials reported a primary outcome consistent with a prospective registration. Prospectively registered trials reported smaller effect estimates (SMD 0.06; 95% CI -0.03 to 0.16) than retrospectively registered (SMD 0.67; 95% CI 0.22 to 1.11) and unregistered trials (SMD 0.59; 95% CI 0.32 to 0.86), and more often defined a single primary outcome, reported sample size calculations, and followed intention-to-treat principles. ConclusionProspective registration and clear primary outcome definition were uncommon in trials comparing exercise therapy after total knee arthroplasty. Trials without these elements had larger effect size estimates at higher risk of bias, suggesting that registration status is an important indicator of methodological quality. Registrationhttps://doi.org/10.17605/OSF.IO/6WZRE Protocol and SAPhttps://osf.io/kwqcb/files/osfstorage