## 4 Discussion  
The aim of the current study was to assess the potential use of electromyography and muscle palpation in identifying early TMJ involvement in JIA patients. These are both routine, non-invasive tests commonly performed during pathological examinations to verify the health of the TMJ. The electromyographic examination, in particular, is a very powerful tool for TMJ diagnosis and has also been proven useful in polysomnographic studies, highlighting a significant relationship between tonic electromyographic pathways in sleeping bruxism episodes and sleep-related breathing disorders [38]. Moreover, the electromyographic evaluation associated with polysomnography could provide important information on sleep habits, which may have implications for the onset of TMJ disorders, as stated by the study by [PERSON] et al. [39]. The results obtained from the interpretation of muscle palpation data suggest that the conditions of masticatory muscles for JIA patients and healthy controls are similar, except for the sternocleidomastoid muscle group, which shows increased pain that persists over time. The same statistical evidence at the SCM level was found by [PERSON] et al. in a study conducted at G. D'Annumzio University in 2019 [18]. As suggested by [PERSON], the sternocleidomastoid is a postural muscle conditioning the balance of the muscles of the stomatognathic system [40]. The significant difference found in pain sensitivity on SCM palpation in JIA patients could, thus, be explained by the postural implications of this muscle. Moreover, the literature demonstrated an increased instability of postural balance in children with JIA [41]. On the other hand, the non-significance of the other palpation values investigated suggests that in JIA patients with no TMJ symptoms and a good rheumatological follow-up, it is possible to maintain palpation values of head and neck muscles comparable to those of healthy subjects. On the contrary, it is reasonable to think that there is a difference in pain sensitivity indices on palpation between patients with and without TMJ involvement. The electromyographic results suggest that the masticatory musculature seems to not be involved in the systemic pathology. The significant difference in IMP values between JIA patients and healthy subjects at baseline is confirmed by a previous case-control study conducted by [PERSON] et al. in 2022, in which the greater muscular activity of the investigated muscles is due to muscular compensation following the joint deficit [42]. Moreover, statistically significant differences in IMP values were found in JIA subjects between baseline and the second examination, showing an improvement in the muscular workload during the clench. However, IMP values for the case and control groups did not show significant differences at TI; this could be attributable to the onset of compensatory mechanisms or growth-related anatomical or drug therapy changes (which were not considered in the current study) occurring between the first and second examinations in JIA patients. Furthermore, comparing the muscle palpation results--subjective examination--and electromyographic examination--objective examination--JIA patients show a higher pain sensitivity of muscles on palpation than the general population, but the instrumental measurement of the head and neck muscle functionality does not confirm these subjective findings. The alteration of pain perception with a decreased pain threshold in JIA subjects was also found in a cross-sectional study conducted by [PERSON] et al., in which JIA patients showed a lower pain threshold even in areas not usually characterized by arthritis [43]. In conclusion, palpation during clinical examination and electromyographic instrumental tests cannot replace the diagnostic gold standard represented by nuclear magnetic resonance.