The disc in the jaw sits behind the jaw bone (mandible) and the head bone (temporal). This particular disc is composed of dense, fibrous connective tissue. For the scientists out there, the collagen fiber distribution is mostly that of types three and one. There is a moderate amount of elastic fibers in the body of the disc with progressively increasing density at the front and back disc attachments. The disc does not have neural innervation (blood vessels) except at the front and back periphery. The posterior attachment or retrodiscal tissue is a very elastic connective tissue structure which is also vascular and innervated. The disc is attached to several structures. The posterior retrodiscal tissue is vascular and innervated. It is termed the bilaminar zone. The elastic nature enables the superior band to store potential energy which can be converted to kinetic energy. Surrounding the retrodiscal tissue is loose areolar connective tissue, adipose tissue, and a plexus of blood vessels which engorge with blood similar to erectile tissues when the disc displaces anterior. This is probably more information than you want to know and suffice it to say, the disc in the jaw is complicated. In physical therapy we have no muscle retrodiscally to bring an anterior disc displacement back into position. Our work is to release the muscles in front, release tight ligaments, balance on the musculoskeletal structures of the head and neck, and work with exercises to get the disc in optimal mechanical position. Ideally, this means that there is no joint noise when opening and closing and that the jaw is capable of full opening (about 3 fingers height).