ABSTRACT
This chapter determines the pathological variations, pathophysiology, course, and probable cause of internal derangement of the temporomandibular joint. The preoperative evaluation consisted of tomographic and arthrographic studies and magnetic resonance imaging in a subgroup of the population. Radiologic and pathological findings were correlated, and a pathological and time-dependent categorisation was employed to correlate and classify clinical, radiologic, and pathological findings into five groups: early, early/intermediate, intermediate, intermediate/late, and late. The early stage cases were characterised by painless clicking and a slightly anteriorly displaced disc. The early/intermediate stage had more intense joint sounds, some pain, and occasional locking. The cause of internal derangements remains unclear but is attributed to trauma rather than occlusal or muscular factors. These are proposed to be manifestations rather than causes of internal derangements. Disc position may be quite variable in asymptomatic individuals. Muscular hyperactivity due to emotional stress, as well as long-standing malocclusion, may become important once articular cartilage breakdown has already started though.
