## 4 Discussion
Easy to use, learnability, motivating, and pleasant are characteristics of this therapy that make it recommendable. Related to knee pain after TKA, our findings suggest that the use of VRBR in rehabilitation protocols effectively reduces it, compared to CT, at post-immediate assessment, and the effect may be maintained at 3 months. On the one hand, our findings about the immediate effect of VRBR agree with [PERSON] (2022) and [PERSON] (2019), although our findings are more robust because we included eight RCTs. On the other hand, the effect of VRBR at 3 months, although disagreeing with [PERSON] (2021) and [PERSON] (2022) (reviews that did not show differences between VRBR and CT at 3 months), must be taken with caution because only two studies provided data for the meta-analysis. Subgroup analysis showed that VRBR is effective alone or combined with CT and that immersive and non-immersive VRBR are effective. However, immersive VRBR is the modality of virtual reality that is more effective in reducing knee pain. Knee pain in musculoskeletal disorders, such as TKA, induces psychological distress, such as mental overload, anxiety, or depression ([PERSON], 2022). The major techniques of CT are passive interventions that do not encourage the patient's participation, motivation, and adherence to the therapy. VRBR induces distraction in these patients. It allows the patients to perform active and rehabilitative exercises due to reduced cognitive attention in pain and avoidance behaviors ([PERSON], 2022; [PERSON], 2022). Distraction induced by VRBR and the regulation of the autonomic system and emotions in the limbic system and hippocampus could be the explanation that supports the fact that patients who performed VRBR increased their pain tolerance in comparison to CT ([PERSON], 2022). Several studies have shown that immersive VRBR may induce more distraction than non-immersive VRBR due to increased parasympathetic activity producing relaxation ([PERSON], 2022). Secondly, our findings showed that VRBR effectively increases knee function at post-immediate assessment and at 3 and 6 months of follow-up. Findings about the immediate effect are a novelty, and the positive effect of VRBR in our review contrasts with the results of [PERSON] (2022), in which there were no differences between VRBR and CT at 3 or 6 months. To assess the effect of VRBR on this variable, our meta-analysis integrates different tests that measure the same construct, knee function, allowing us to include more RCTs in the analysis and increase the level of evidence. In this case, it is difficult to choose if VRBR is more effective when it is used alone or combined with CT due to similar subgroup analysis findings (\(\text{SMD}=-0.64\) and \(\text{SMD}=-0.52\) for VRBR vs. CT and VRBR plus CT vs. CT, respectively). In addition, the same value was obtained with immersive than with non-immersive VRBR on knee function. Although both seem to be equally effective, performing virtual exercises using non-immersive virtual reality devices such as the Nintendo Wii or Kinect may be recommendable for these patients, especially in patients that do not tolerate the possible adverse events of immersive VRBR. One important sequela of OA and TKA is balance disorders. In this meta-analysis, the studies included only data from dynamic balance assessment, and our findings showed that VRBR is effective at increasing dynamic balance. This result coincides with [PERSON] (2019), but it is opposite to [PERSON] (2022), which shows no effect of VRBR on dynamic balance at post-immediate assessment and at 3 months of follow-up. Subgroup analysis according to a specific use of VRBR showed that the isolated use of VRBR and combined VRBR with CT effectively increased dynamic balance, although the effect was major when VRBR was used alone. Finally, non-immersive VRBR is an adequate option to improve dynamic balance in these patients, informing clinicians that to increase dynamic balance, a good therapeutic option could be the combination of non-immersive VRBR with CT.