What does this mean?
The rounded bony head at the end of the lower jaw slides forwards out of its socket when you open your mouth and comes back as you close. When you open very wide, this head can move in front of the bony ridge ahead of it, and the way back closes off. The mouth stays open and the teeth do not meet at all.
The distinguishing point is the direction. The problem here is not being able to close your mouth. If you struggle to open your mouth but can close it comfortably, the situation is different and does not carry the same urgency. If your speech has become hard to understand, you cannot hold your saliva and your back teeth do not touch at all, the picture fits a jaw that is stuck open.
Time is decisive here. The longer the jaw stays open, the more the surrounding muscles contract, and the more they contract, the harder it becomes for the bony head to return to its place. A situation that can be resolved by hand with a manoeuvre in the early hours may, as time passes, need help from medication or other methods.
The jaw is often left stuck open during an ordinary movement; yawning, keeping the mouth open for a long time, being sick or biting into a large mouthful are the beginnings people describe most often.
Likely causes
What helps at home?
- Do not try to put your jaw back in place yourself until you reach the clinic or the emergency department; forcing it can damage the joint and the ligaments.
- Do not open your mouth any further, talk less, and do not eat or drink anything.
- Support your jaw gently with your hand on the way; resting your head on a pillow may reduce the muscle tension.
- If this is not the first time, be ready to say how it was put back before and which medicines you take.
- If you cannot close your mouth at all, seek help without waiting
- Difficulty swallowing or breathing
- The situation starting after a blow, with bleeding or numbness alongside it
- Marked swelling or bruising on one side, or bleeding from the ear
- The same situation happening again at short intervals
Frequently asked questions
- Will it go back into place on its own?
- Sometimes the mouth stays open only briefly and the jaw closes on its own once the muscles relax. If it is not closing, waiting does not help; as the surrounding muscles contract, putting it back becomes harder. For that reason it is advised that you are seen the same day.
- Why did it happen while I was yawning?
- Yawning is one of the movements in which the jaw opens widest. In people whose joint ligaments are loose, or after a procedure in which the mouth was kept open for a long time, this limit can be passed more easily. Yawning on its own is not a sign of disease, but how the episode started does help with the assessment.
- Can it happen again once it has been put back?
- There is a chance of it recurring, particularly in the weeks after the first episode. That is why you are asked to avoid opening wide for a while, to support your jaw with your hand when you yawn and to stay away from hard mouthfuls. Where it recurs, the joint may need to be assessed separately.
This content is for general information and does not replace an in-person examination. Symptoms overlap between conditions, and a diagnosis can only be made clinically.