The clinical diagnosis of a Temporomandibular Disorder (TMD) has traditionally been based on data gathered by means of a medical history and physical examination. The most common signs and symptoms associated with TMD are reduced jaw opening, pain and elevated tenderness in the muscles of mastication, pain and elevated temporomandibular joint (TMJ) tenderness, and TMJ noises upon movement. These signs and symptoms are routinely detectable by a skilled clinician upon examination. Unfortunately, the clinical problem described globally as a TMD has several different and overlapping patho-physiologic disease processes, and a traditional clinical examination does not provide highly tissue-specific pathologic information. Were it readily available, such information would be greatly useful, since logical and accurate treatment planning requires that each disease process be correctly identified. One important challenge for researchers interested in TMD will be the careful definition and subsequent validation of diagnostic methods which identify the relevant ongoing pathological disease process. On such research area, which has great promise, is the establishment of a valid diagnostic technique for intracapsular pathologies unique to TMD patients. This paper provides a critical review and discussion of the diagnostic validity of TMJ arthroscopy and other related methods of identifying intracapsular pathologies associated with TMD.