An acute TMJ closed lock occurs when the jaw has limited opening from the closed position. This can occur after the jaw joint has been making clicking and popping sounds for quite a while. A closed lock can be caused by muscle tightness and/or the disc in the temporomandibular joint being in the way of the jaw opening. Pain can occur when you try to open your mouth from this closed-lock position.
Sometimes there is a bit of warning before the mouth gets stuck in the closed position. This warning could be episodes where the jaw locks and then unlocks. In some situations, however, the jaw gets stuck in the closed position without any warning.
If your jaw gets stuck in the closed position it is important to visit a properly trained dentist within a week of the first occurrence. This will help you to recapture the TMJ disc and return to normal jaw function. As time goes by, however, the TMJ disc will deform and will become stuck, or it will adhere to the new closed-lock position. When this happens, the situation will deteriorate into a chronic TMJ closed lock where it is much more difficult to recapture the TMJ disc.