COMT and arthritic joint disease: This multi-etiological approach covers a wide range of etiological causes, including macro-traumas or micro-traumas in the para-functions (i.e. bruxism), skeletal and occlusal alterations (which according to the literature have decreased in this type of disorder in recent years), systemic factors (arthritis, alterations in collagen metabolism, etc.), masticatory and cervical muscle hyperactivity, alterations of the collagen matrix in temporomandibular joint (TMJ) cartilage, hormonal factors especially in women, and genetic factors, primarily catechol-o-methyltransferase (COMT).