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

BACKGROUND AND PURPOSE: Prospectively registering the primary trial outcome is important to reduce selective outcome reporting and increase the trustworthiness of findings, which guide clinical practice. The objectives of our systematic review were to explore and compare the reporting characteristics of prospectively and non-prospectively registered trials investigating exercise therapy following total knee arthroplasty.

METHODS

Randomized trials comparing effects of exercise therapy after total knee arthroplasty for osteoarthritis were identified in 4 databases from 2000 to August 12, 2024. One primary outcome per trial was extracted, using a pre-specified hierarchical algorithm, irrespective of outcome domain. Pooled standardized mean differences (SMDs) were calculated on pre-specified outcome domains, and risk-of-bias assessed using the Cochrane Risk-of-Bias tool v2.

RESULTS

94 trials, comprising 9,396 participants, were included, of which 13 were prospectively registered, 33 retrospectively registered, and 48 unregistered. A single primary outcome was defined in 44% of the 94 trials, and 4 trials reported a primary outcome consistent with a prospective registration. The pooled SMD of primary outcomes was 0.06 (95% confidence interval [CI] -0.03 to 0.16) for prospectively registered trials, 0.67 (CI 0.22-1.11) for retrospectively registered trials, and 0.59 (CI 0.32-0.86) for unregistered trials. Lower risk-of-bias ratings and higher proportions of intention-to-treat adherence, dropout reporting, and adverse event reporting were observed among prospectively registered trials.

CONCLUSION

Among prospectively registered trials we showed smaller effect size estimates between interventions with lower risk-of-bias ratings, and higher proportions of intention-to-treat adherence, dropout reporting, and adverse event reporting in contrast to trials without prospective registration; furthermore, clear specification of a single primary outcome was uncommon among trials evaluating exercise therapy after total knee arthroplasty.