Conducting randomized clinical trials (RCTs) with a comparator group is methodologically appropriate and essential to minimize confounding factors in systematic reviews, provided that the interventions, including Usual Care (UC) in the comparator group, are described in detail to ensure the reproducibility of the methods.

To evaluate the quality of the description of interventions termed UC as a comparator group in RCTs that utilized exercise for the treatment of knee osteoarthritis (OA).

A meta-research study with a systematic review of RCTs involving exercise for knee OA in individuals aged 40 years or older. Searches were conducted in the following databases: MEDLINE, EMBASE, Cochrane Central, PEDro, CINAHL, and SportDiscus. Studies that compared any therapeutic exercise to Usual Care were included. The description of interventions in both the exercise intervention group and the UC control group was assessed using the Template for Intervention Description and Replication (TIDieR) tool. A quantitative and qualitative comparison was made regarding the quality of reporting between the groups, as well as the description before and after the publication of the TIDieR checklist.

A total of 67 RCTs were analyzed, and in 100% of these RCTs, the description of the UC group was of low quality. The TIDieR score (0-12) was higher in the exercise group, with a median of 4.0 (interquartile range [IQR] 3 to 5), compared to the UC group, which had a median of 1.0 (IQR 1 to 2), p < 0.001. For the intervention groups, only 22.3% of the descriptions were considered "high quality." There was no difference in the quality of intervention descriptions before and after the publication year of the TIDieR checklist.

The description of interventions referred to as UC in RCTs involving exercise for knee OA is insufficient. Consequently, it is not possible to replicate these RCTs or properly implement their findings in clinical practice.

These findings underscore the need for clearer and more consistent descriptions of groups in RCTs on knee OA, particularly regarding the UC group. Furthermore, it is essential to encourage the adoption of the TIDieR checklist to ensure transparency and reproducibility in these studies.