Unpacking the Comparator: Mapping “Usual Care” in Non-Surgical Knee OA Trials

Objectives “Usual care” is a common comparator in randomized trials (RCTs) evaluating interventions for knee osteoarthritis (OA), but it lacks a standardized definition. This scoping review aimed to systematically map how usual care has been defined and reported in knee OA RCTs, with attention to the terminology, components, and adherence to reporting standards.

Methods We searched MEDLINE, EMBASE, CENTRAL, CINAHL, and the ClinicalTrials.gov registry from inception to May 2025 for trials involving adults with knee OA that compared a non-surgical intervention to usual care (or similar terms). Paired reviewers independently screened citations and extracted study characteristics, terminology used to describe and components of usual care, care setting, OA severity and diagnosis, intervention type, and references to external guidelines. We summarized findings and assessed reporting quality using the Template for Intervention Description and Replication (TIDieR) and Consensus on Exercise Reporting Template (CERT) checklists, where applicable.

Results Of 11804 citations screened, we identified 154 RCTs across 33 countries. “Usual care” was the most frequently used descriptor term (53.9%), with definitions that varied considerably. While 68.2% of trials provided detailed descriptions, nearly one-third offered only vague or minimal information. Only 22.7% referenced external guidelines. Usual care content ranged from minimal care to complex multimodal packages, with substantial variation by intervention type. Reporting quality was suboptimal: trials addressed, on average, just over half of TIDieR and approximately two-thirds of CERT checklist items. Usual care often lacked transparency, standardization, and reference to best practice recommendations.

Conclusion One in 3 knee OA trials using usual care as a comparator did not provide a clear, detailed definition of “usual care.” Variability in usual care definitions and reporting compromise trial validity, limit evidence synthesis, and hinder clinical translation. There is an urgent need for standardized and detailed reporting of usual care interventions in knee OA trials.