Association between generalized joint hypermobility and temporomandibular disorders: a review of the literature

Aim: Temporomandibular joint disorders (TMD) have a multifactorial etiology. Joint Hypermobility (JH) is an increase of joints mobility over physiological limits and has been reported as a predisposing factor to the development of signs and symptoms of TMD. The term Generalized joint hypermobility (GJH) used when multiple joints are affected. A relationship between TMD and GJH has been suggested in numerous studies and the supposed sequence of events in this association is that the temporomandibular joint (TMJ), among the hypermobile joints, caused by a looseness of the ligaments, may lose the physiological relationship between condyle and the Glenoid fossa and be overloaded, resulting in degenerative changes which may become manifest as internal derangements and/or inflammation. The purpose of this study is to get a literature review focused on the association between JH and TMD. Methods: We conducted an electronic search using PubMed and Cochrane Library from 2000 to 2018. The keywords used were: Temporomandibular joint disorder AND generalized joint hypermobility AND joint laxity AND assessment methods AND diagnostic criteria AND reproducibility. Papers were included in the analysis if the study population was clinically relevant, there was a group control and the GJH was assessed with the Beighton score. Only articles written in English were included in the study. Case reports have been excluded. Results: Search returned 58 results, on the basis of the relevance were selected 21 studies. Some studies found a significant positive association between TMD’s signs and symptoms and GJH (p<0,05), while other studies could not demonstrate a statistically significant relationship (p>0,05). Numerous studies present in literature reported the prevalence of TMDs is higher in subjects with symptoms of articular hypermobility suggesting that GJH would be a risk factor positively associated with TMDs. Contrarily, other authors suggest that there is no clear evidence of the association between JHS and TMDs and indicate that one limit could be the relatively small number of patients enrolled in these studies. Conclusion: Based on the results of this research, even if many articles reported an association between GJH and TMD, the exact relationship between GJH and TMDs has not been established yet. This lack of conclusiveness also may be due to: the use of different clinical assessment methods of GJH and that among the different authors which use the Beighton score there is a lack of consensus of a GJH diagnostic cut off level and that there isn’t a protocol of the performance of the test; that GJH is influenced by age, gender and ethnicity; and different diagnosis methods of TMD. All these factors can limit the ability to make cross-study comparisons. A clinical relevance is that Hypermobility of the joint is not a modifiable risk factor but individuals with TMD associated with GHJ should be carefully evaluated by inter-disciplinary specialists as these factors could change the therapeutic approach and may eventually have impact on the prognosis of TMDs. Also, patients with GJH should be counselled regarding the possible effects of joint laxity on the TMJ and a simple screening with Beighton test makes possible to: teach patients preventive measures based on functional self-control and self-limitation; make caution during therapy; inform the patient of his/her predisposition for intra-articular pathology before undertaking any type of mouth or jaw therapy.