Why does the jaw joint click or lock?

The jaw joint, known clinically as the temporomandibular joint (TMJ), sits about a centimetre in front of the ear canal; it is one of the two joints that connect the lower jaw to the skull. Conditions that affect this joint and the chewing muscles that work it are known together as a TMJ disorder. Noise, pain and restriction are different signs within this group; they do not always come together, and each carries its own level of seriousness.

A click or crackle happens at the moment the disc inside the joint slides against the joint head during movement. If there is no pain, your mouth opens to a normal width and the jaw does not shift to one side, dentists generally do not count this noise as a sign of an urgent problem; in many people it carries on for years without leading to any other issue. It is not the noise itself but whether pain or restriction is added to it that needs watching.

Locking can be seen in two different forms. In some cases, the disc inside the joint slips forward and blocks the jaw from opening; you cannot open your mouth past a certain point. In other cases, the opposite happens: after opening wide, the jaw cannot close again; this is a form of jaw dislocation. If either does not resolve on its own within a few minutes, it needs to be assessed the same day.

The most familiar cause of morning jaw pain is a teeth-clenching or grinding habit you are not aware of during sleep. Throughout the night, the chewing muscles repeatedly carry a load they never meet in normal chewing; when you get up in the morning, your jaw feels tired, your temples are tender, and sometimes a headache comes with it. As the muscles relax through the day, the pain usually eases. Flattened tooth surfaces and unexpectedly broken fillings and crowns are the marks this habit leaves in the mouth.

Missing or badly worn teeth contribute to this picture from a different angle. When back teeth are missing or wear progresses, your bite height drops, and the lower jaw has to move further up and back than it should on closing. This altered position places extra load on the jaw joint and the muscles around it; over time, it can make the noise and pain worse.

The most common mistake at home is deliberately trying to click the jaw, or trying to ease the joint by chewing gum constantly; both increase the load on the joint instead of reducing it. Another mistake is trying to force a locked jaw open; this can push the disc into a more advanced position.

Most of this picture settles on its own with patience and simple measures. But if the locking keeps recurring, the jaw keeps shifting permanently to one side, or the pain carries on despite weeks passing, imaging and a specialist assessment are needed; there is no benefit in putting this step off.

The points on the left show a picture that mostly settles on its own or with a simple measure; those on the right show one that needs assessing the same day or soon after.

For a jaw joint noise or locking, the place to go is your dentist; they refer you to oral surgery or physiotherapy if needed. This page does not replace that visit.

1. 1

   The history

   You are asked when the noise started, whether there is pain, whether it is worse in the morning or the evening, whether you are going through a stressful period and whether you have a teeth-clenching habit.

2. 2

   Measuring mouth opening, and palpation

   How many millimetres your mouth opens is measured, and tender points are looked for by pressing a finger over the joint and on the temple and cheek muscles.

3. 3

   Assessing your bite and wear

   How your teeth meet when you bite together, flattened chewing surfaces and missing teeth are looked at; these show whether your bite height has changed.

4. 4

   Imaging if needed

   If the locking keeps recurring or the findings are not clear, an MRI scan can be used to assess the position of the disc inside the joint; a plain X-ray or a panoramic only shows the bone structure.

5. 5

   The outcome, and what happens next

   Depending on the findings, a night guard, physiotherapy, stress management or replacing missing teeth may come up. Surgery is only discussed when other methods have not been enough.

There is no single treatment for this complaint; what is done depends on whether the noise, the locking or the clenching is the dominant feature.

The points below show what the common mistakes in this situation actually make worse.

How long it takes is measured in weeks rather than days for most of this picture.

1. The first two weeks

   A soft diet, avoiding opening your jaw very wide (yawning, big bites) and applying warmth can noticeably ease the pain within this time. If this does not bring enough relief, you need to be assessed.

2. A few weeks with a night guard

   Morning pain from teeth clenching noticeably eases within a few weeks of using a night guard; morning jaw tiredness is usually the last symptom to improve.

3. After a closed lock

   Pain and tenderness can last a few days after manual reduction; continuing with a soft diet during this time reduces the risk of locking again.

4. After missing teeth are replaced

   It takes time for the reduced load on the joint to follow from regaining your bite height; the change in noise and pain is seen gradually over weeks.

Because most cases progress with a night guard and simple measures, the cost is usually limited; the scope grows when imaging or replacing missing teeth comes into it. These are the items that determine the scope:

Whether imaging is needed

Imaging is not needed in simple cases; an MRI scan comes into it if the locking keeps recurring.

The type of night guard

A custom-made night guard taken from an impression and a ready-made one differ in cost and effect.

Whether there are missing or worn teeth

If restoring your bite height is needed, this means a more extensive plan than a night guard alone.

Whether physiotherapy is needed

In some patients, physiotherapy sessions become part of the process alongside dental treatment.