## 4 Discussion
### Mt  
First, it should be noted that the meta-analysis conducted with studies including MT vs. control and evaluating the VAS immediately after the intervention showed a moderate effect in favor of the MT intervention compared to the controls (effect size = 0.799, IC 95%= 0.171 to 1.427; \(p\) = 0.001). The heterogeneity among the studies was considerable. The studies included in the meta-analysis used both joint mobilization [30; 32; 35] and massage techniques [33; 36] and included different dosages. Two studies [30; 33] showed a treatment effect in favor of the MT intervention. It should be noted that the study showing the greatest benefit was an 8-week program [33]. Concerning the studies that showed no effect in either direction, two of them included only one session [35; 36]. Therefore, the dose of the intervention may be relevant to the reduction in pain as measured by VAS. No differences were found between the studies in the sample population, most of which included participants with KO grade \(\geq\) II. Considering the results of the meta-analysis and the high level of evidence provided by the GRADE tool, the use of manual therapy for short-term pain reduction as measured by VAS can be recommended. On the other hand, the evidence for the effects of MT on other pain outcomes is very low or low. The heterogeneity of the studies, the outcomes protocols, and the limited number of publications did not allow for performing a meta-analysis. PPT of the knee was the second most commonly evaluated post-operative outcome, with some studies showing a benefit for TM [30; 34; 35] and others not [36]. This may be due to several reasons, not only related to the interventions themselves, but also to the lack of uniformity in the PPT assessment protocol, along with the fact that some of the participants in the studies may have had some form of central sensitization, which can alter PPT [51]. The MT showed (very low evidence) benefit for the NPRS [31] and the WOMAC pain subscale [33]. Four studies [30; 33; 34; 35] were followed up, but inconsistencies in the follow-up and the use of different measures prevented a meta-analysis. The results suggest that TM does not reduce pain during follow-up, but the level of evidence is low/very low. [PERSON] et al. [52], in a systematic review published in 2021, found that MT can reduce pain in the short term. However, this systematic review did not include meta-analyses. It should be noted out that [PERSON] et al. [53], who conducted a systematic review and meta-analysis in 2018, reported that the reduction in VAS score in orthopedic manual therapy compared to control interventions was not statistically significant (SDM: \(-\)0.59; 95% CI: \(-\)154 TO \(-\)0.36; \(p\) = 0.224). They only included two studies in the meta-analysis, and the studies included in our systematic review and meta-analysis were published after 2018. On the other hand, they found a significant improvement in VAS score when MT was compared with exercise therapy (SDM: \(-\)0.78; 95% CI: \(-\)1.42 to \(-\)0.17; \(p\) = 0.013). The effect size was moderate, as we found in our meta-analysis. Regarding the WOMAC pain subscale, [PERSON] et al. [53] also showed that the MT improved pain compared to controls (SDM: \(-\)0.79; 95% CI: \(-\)1.14 to \(-\)0.43; \(p\) = 0.001). These results are in line with those of [PERSON] et al. [54], who reported significant effects (SDM: \(-\)0.61; 95% CI: \(-\)0.95 to \(-\)0.2; \(p\) = 0.0003). The literature on MT without combining it with exercise or other treatments for KO is scarce, although it has increased in recent years. [PERSON] et al. [54] noted the same difficulty in determining results due to the lack of good quality studies on the subject, but predicted that MT may be a safe and effective therapy to reduce pain in patients with KO [54]. MT with exercise has previously been shown to improve function as well as pain [53; 55]. Our review also shows that the use of TM without exercise also produces improvements in pain, which is consistent with the results reported by [PERSON] et al.