What is it?
In the jaw joint there is a small cushion called the disc, sitting between the condyle at the top of the lower jaw and its socket in the temporal bone. Normally the disc rests on the condyle and slides forward with it as the mouth opens. In disc displacement the disc lies in front of the condyle while the mouth is closed.
If the disc slips back into place as the mouth opens, a click is heard as the condyle moves onto it; a second sound may come as the mouth closes. This is called displacement with reduction. If the disc does not slip back into place, it blocks the path in front of the condyle and the mouth stops opening beyond a certain point; the jaw shifts towards the affected side as you open, and the sound you used to hear disappears.
Not every joint that makes a sound needs treatment. A click that is painless and does not limit opening is most often simply monitored. What changes the picture is pain being added, catching becoming more frequent and the start of a period in which the mouth will not open; the time that passes in that period may play a part in whether the limited movement becomes settled.
Signs
You will not necessarily have all of these at once.
Why does it happen?
- 01
Loosening of the ligaments and repeated strain
The ligaments that hold the disc in place can lose their elasticity through repeated wide opening. Long procedures inside the mouth, large mouthfuls and wide yawns are what that strain looks like in everyday life.
- 02
A change in the load on the joint
Constant clenching, chewing on one side and gaps left by missing back teeth change the pressure the condyle puts on the disc. Once the balance of load is disturbed, it becomes harder for the disc to hold its position.
- 03
Trauma
A blow to the jaw or the head, sudden neck movements and procedures carried out with the mouth held open for a long time can disturb the relationship between the disc and the condyle. Symptoms starting after a particular event is a clue in this direction.
- 04
The shape of the joint and general joint laxity
A shallow socket, and ligaments that are lax throughout the body, make the disc less stable. This condition has been reported more often in people who describe excessive movement in their fingers and other joints.
How does it progress?
- 1
Displacement with reduction
The disc slips back into place as the mouth opens; a click is heard and opening is usually normal. There may be no pain, and the picture can stay the same for many years.
- 2
Intermittent catching
The jaw catches from time to time; you have to move it slightly or shift it sideways to open your mouth. Catching that becomes more frequent is taken as a warning of the next stage.
- 3
Locking (acute phase without reduction)
The mouth suddenly opens only a limited amount, the jaw shifts towards the affected side as you open and the old sound disappears. Dealt with early, the chance of regaining movement is higher.
- 4
Adaptation phase
Over months the opening may partly increase; even though the disc does not slip back into place, the joint adapts with the surrounding tissues. If changes begin on the joint surface, a grating sound can be added to the picture.
How is it treated?
In newly started locking the aim is to regain movement early. After the examination, and imaging if it is needed, your dentist may try to move the disc back into place by hand; then come a soft diet, avoiding wide opening and the opening exercises your dentist shows you. Any decision about medication to reduce the pain and the oedema inside the joint is for your dentist to make.
In joints that make a sound but cause no pain or restriction, the approach is monitoring and managing the load. Grinding down teeth, permanently changing the bite or starting orthodontic treatment in order to silence the sound is not an expected route in this condition. If you clench in your sleep, a splint may be considered to reduce the load on the joint.
Where restriction has lasted a long time and has not responded to conservative care, options such as washing out the joint are assessed in oral and maxillofacial surgery; open joint surgery is kept for selected cases. Before any procedure it should not be overlooked that muscle pain is a separate condition and is managed separately.
- Your mouth suddenly opening less than the width of a finger and staying that way for days
- The jaw staying open and not closing
- Restriction, a change in your bite or numbness that starts after a blow
- Swelling, redness and a fever around the joint
How is it prevented?
- Put your hand under your chin while you yawn to limit how far it opens, and cut large mouthfuls in half.
- Ask for breaks during long dental treatments; holding the jaw open without a pause strains the joint.
- Avoid moving your jaw over and over to test whether the sound is still there.
- Do not leave gaps from missing back teeth for a long time, and keep to your regular check-ups.
Frequently asked questions
- Is the sound from my jaw dangerous?
- A click that causes no pain and does not limit how far your mouth opens is not in itself an emergency; it is common in the population and is most often simply monitored. What to watch for is a change in the character of the sound, catching becoming more frequent, pain being added, or the sound disappearing and the mouth becoming unable to open. A sound like grit rubbing points to a different condition.
- My jaw has locked, how long can I wait?
- If the locking is new and has happened for the first time, having it assessed within a short time is preferred to waiting for it to pass. The chance of regaining movement is higher in the early phase; as time goes on the surrounding tissues adapt to the new situation and the restriction can become settled. In the meantime you will be asked to avoid opening wide and to keep away from hard foods.
- Does the disc slip back into place on its own?
- In some people the disc may settle back into place over time; in others it does not, but opening and comfort can still improve because the joint adapts. So symptoms easing does not always mean the disc has returned to its place. Because of this uncertainty, treatment decisions are made on pain and function rather than on the sound.
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.