The term "internal derangement" has been used for more than a century in surgical and orthopedic literature to describe conditions that interfere with normal joint function. Earlier TMJ internal derangement was perceived as a mechanical problem and interventions at repositioning the displaced disc were advocated. Over the past few decades, there has been a conceptual shift from internal derangement and disc displacement being a primary diagnosis toward our current understanding that disc displacement is an endpoint of a process in which there is damage to articular tissues and biomechanical...