Internal derangement (ID) of the TemporoMandibular Joint (TMJ) is a general orthopedic term implying a mechanical fault that interferes with the smooth action of a joint. Athroscopy and arthrocentesis of superior TMJ compartment are among the commonly used diagnostic and minimally invasive treatment modalities for ID. Arthrocentesis has been considered as the cheaper, simpler and blind substitute for arthroscopy. This study reports arthroscopic outcomes that defy this understanding, and presents a new arthroscopic finding in ID patients: "Capsular Migration"; which changes the criteria of a successful entry into the superior TMJ compartment.