Internal Derangement of the Temporomandibular Joint: New Perspectives on an Old Problem.

Internal derangement is caused by loss of the structure and function of the intra-articular tissues, leading to a failure in the biomechanics of the temporomandibular joint. This tissue failure is usually caused by joint overload, leading to an inflammatory/degenerative arthropathy of the temporomandibular joint. The intra-articular changes associated with internal derangement of the temporomandibular joint can also be caused by a systemic arthropathy or a localized atypical arthropathy involving the temporomandibular joint. Clinicians must be diligent in establishing the correct diagnosis and cause of the internal derangement, which ultimately leads to the appropriate management of patients with these disorders.