Tendinopathy of masticatory muscles: a narrative review on the potential pathogenetic mechanism and pain characteristics.

OBJECTIVES: Within the classifications of temporomandibular disorders (TMD), myofascial pain is the term used to describe the presence of pain arising from the fascia, at the level of the masticatory muscles. Additionally, myofascial pain has been traditionally divided into localized myofascial pain and myofascial pain with referral, to indicate the presence of pain in areas that are not in anatomical contiguity with the ones palpated. Nonetheless, these terms nowadays appear to be in contrast with the clinical finding that pain elicited upon masticatory muscle palpation is often reported at the level of the tendon insertions rather than the muscle tissue itself. MATERIALS AND METHODS: The article provides an overview of how, from a cellular level point of view, tendinopathy occurs in the masticatory muscles, focusing on the neuroplastic and vascular changes that are secondary to the impaired healing process. RESULTS: The present narrative review provides a hypothesis of a possible pathophysiological mechanism that can explain why the masticatory muscle tendons are the first structures to be affected by the mechanical overloading in TMD patients. Additionally, the review provides insights regarding the possible mechanism that can explain the onset of sensitization, responsible for pain experience in areas distinct or distant from the site of palpation. CONCLUSIONS: The paper presents the clinical implications of masticatory muscle tendinopathy, presenting some clinical recommendations based on the current guidelines for the treatment of TMDs. CLINICAL RELEVANCE: The palpation of the masticatory muscle’s tendon insertions allows clinicians to better evaluate the presence of TMD-related pain compared to the palpation of the main muscle tissue.