The temporomandibular joint (TMJ), located just in front of the lower part of the ear, allows the lower jaw to move. The TMJ is a ball-and-socket joint, just like the hip or shoulder. When the mouth opens wide, the ball (called the condyle) comes out of the socket and moves forward, going back into place when the mouth closes. TMJ becomes dislocated when the condyle moves too far and gets stuck in front of a bony prominence called the articular eminence. The condyle can't move back into place. This happens most often when the ligaments that normally keep the condyle in place are somewhat loose, allowing the condyle to move beyond the articular eminence. The surrounding muscles often go into spasm and hold the condyle in the dislocated position.