Why Does My Jaw Click? The Biomechanics of TMJ Popping and Disc Displacement

Jaw clicking can happen while chewing, speaking, yawning, or opening the mouth. It may occur without pain, while in other cases it appears with stiffness, tenderness, catching, or limited movement.

To understand why your jaw clicks, it helps to look at the temporomandibular joint, or TMJ. This joint allows the lower jaw to perform both hinge-like rotation and sliding movement as the mouth opens and closes.

Inside the joint, an articular disc sits between the mandibular condyle and the temporal bone. One common cause of clicking is disc displacement with reduction, where the disc is displaced from its usual position when the mouth is closed and moves into a more functional relationship with the condyle during opening, producing a click or pop.

However, a jaw click does not automatically confirm disc displacement or joint damage. Painless clicking is common and often does not require treatment. Pain, locking, restricted opening, or changes in jaw movement are more important signs that further assessment may be appropriate.

The Anatomy of a Click: Kinematics of the Condyle-Disc Assembly

A jaw click often occurs during a brief change in the relationship between the mandibular condyle, the articular disc, and the temporal bone as the jaw moves.

The temporomandibular joint does not function as a simple hinge. During opening, the mandibular condyle both rotates and translates, or slides forward, while the articular disc normally remains coordinated with the condyle as the joint moves along the articular surface of the temporal bone.

Changes in this coordination can produce an audible click or pop.

What is anterior disc displacement with reduction?

The articular disc is a dense fibrocartilaginous structure positioned between the mandibular condyle and the temporal bone. In its typical relationship, the thinner intermediate region of the disc lies between the articulating surfaces during movement.

In disc displacement with reduction (DDwR), the disc is displaced relative to the condyle when the mouth is closed but returns to a more typical relationship with the condyle during opening.

The most common pattern is anterior disc displacement with reduction (ADDwR), meaning the disc lies farther forward than expected when the jaw is closed.

The word “reduction” does not refer to reducing inflammation or shrinking the disc. In this context, it means that the displaced disc returns to a functional relationship with the condyle during movement.

What Actually Produces the Click?

As the mouth begins to open, the condyle moves through a combination of rotation and forward translation.

When a disc is displaced anteriorly, the condyle may initially move behind the disc rather than remaining in its usual relationship with the intermediate portion of the disc.

As opening continues, the condyle and displaced disc can rapidly change their relative position, with the disc moving into a more functional relationship with the condyle. This abrupt change in condyle-disc mechanics is associated with the characteristic opening click.

The sequence can be simplified as:

Mouth Closed

Disc displaced relative to condyle
↓
Jaw Begins to Open

Condyle rotates and translates forward
↓

Disc Reduces

Condyle and disc re-establish a more functional relationship
↓

Click or Pop May Occur

After reduction, the jaw can generally continue opening without the mechanical limitation associated with a non-reducing disc displacement.

Why can the jaw click again when closing?

Some people experience both an opening and a closing click.

During closing, the condyle moves back toward its resting position. In a joint with disc displacement with reduction, the disc may again lose its reduced relationship with the condyle as the jaw closes.

This can create a second, often softer click.

When an opening and closing click occur as part of the same movement cycle, the pattern has historically been described as reciprocal clicking.

Not every person with disc displacement has an obvious click in both directions, and the timing or intensity of the sound can vary.

Is the disc really “popping back into place”?

“Popping back into place” is useful shorthand, but it can create the wrong impression.

Reduction does not necessarily mean that the disc has permanently returned to its original anatomical position. It means that the condyle and disc temporarily regain a more typical functional relationship during that part of jaw movement.

When the mouth closes, the disc may again become displaced relative to the condyle.

This distinction helps explain why clicking can happen repeatedly during everyday opening and closing.

Does every click mean the disc is displaced?

No.

Disc displacement with reduction is strongly associated with clicking, popping, and snapping sounds, but joint noise alone cannot establish the exact internal position of the disc.

Under the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD), clinicians assess the pattern of joint sounds during repeated opening, closing, lateral, and protrusive movements. Even these clinical criteria have limitations when compared with imaging.

When confirmation of disc position would meaningfully affect diagnosis or management, magnetic resonance imaging (MRI) is the principal imaging method for evaluating the articular disc and other soft tissues within the TMJ.

For many people with painless clicking and normal jaw function, however, imaging is not automatically necessary.

A Click is a mechanical event, not automatically tissue damage

The presence of a click indicates that something about joint movement is producing an audible mechanical event, but the sound itself does not establish that the joint tissues are deteriorating or that the joint is progressing toward degenerative disease.

Disc displacement with reduction is frequently painless. Longitudinal evidence also suggests that many cases remain stable rather than progressing predictably toward persistent locking.

This is why clinical assessment focuses on the whole pattern of joint function, including pain, locking, range of motion, movement quality, and changes over time, rather than the sound alone.

Potential Drivers and Risk Factors: Why the Jaw Disc May Shift

Disc displacement within the temporomandibular joint is unlikely to result from one isolated cause. Research has proposed several contributing factors, including repetitive mechanical loading, trauma, joint anatomy, ligament or capsular laxity, changes in disc morphology, and degenerative joint changes.

For many people, however, the exact reason a disc changes position cannot be identified with certainty.

Repetitive Loading and Bruxism: The Micro-Trauma Pathway

Repeated jaw loading is frequently discussed as a potential contributor to temporomandibular joint symptoms.

Bruxism includes both awake clenching and sleep-related grinding or clenching. These behaviours can place substantial repetitive loads on the teeth, masticatory muscles, and temporomandibular joints.

Research has found an association between bruxism and TMD, but that does not establish that bruxism directly causes the articular disc to move forward.

In particular, the evidence does not justify a simple sequence such as:

Grinding → stretched disc ligaments → anterior disc displacement

The relationship is likely more complex. Repetitive loading may contribute to symptoms or tissue stress in susceptible individuals, while many people with bruxism never develop symptomatic disc displacement.

Patients who notice nocturnal clenching and grinding may therefore benefit from having the behaviour and its effects assessed, particularly when it is accompanied by tooth wear, muscle soreness, jaw pain, or other symptoms.

Also Read: Jaw Clenching, Bruxism and Muscle-Related TMD Care in Vancouver

August 17, 2025

What About the Lateral Pterygoid Muscle?

The lateral pterygoid is an important muscle involved in jaw movement and coordination of the condyle-disc complex.

Older explanations of TMJ clicking sometimes proposed that a tight or spasming lateral pterygoid muscle actively pulls the articular disc forward, producing anterior disc displacement.

That model is now considered too simplistic.

Anatomical studies show that the superior portion of the lateral pterygoid has variable relationships with the TMJ capsule, disc, and condylar neck. Recent histological research found that most fibres of the superior head of the lateral pterygoid inserted into the condylar neck, while relatively few inserted directly into the articular disc.

For that reason, phrases such as “lateral pterygoid muscle spasm” should not be treated as a stand-alone explanation for why a disc becomes displaced.

Altered muscle activity may influence jaw mechanics and symptoms, but current evidence does not support the claim that stress or bite problems routinely cause the lateral pterygoid to spasm and physically pull the disc out of position.

Occlusal Instability and Bite Alignment

The relationship between the bite and temporomandibular disorders has been debated for decades.

Historically, uneven tooth contacts, missing posterior teeth, and malocclusion were often considered major causes of TMD. Contemporary evidence is much more cautious.

The National Institute of Dental and Craniofacial Research states that current research does not support the belief that a “bad bite” or orthodontic treatment causes TMD. Systematic reviews have likewise found that associations between individual occlusal features and TMD are inconsistent and generally insufficient to establish a cause-and-effect relationship.

This means it would be inaccurate to say that an uneven bite routinely forces the jaw into compensatory movements that eventually displace or wear down the disc.

Occlusion can still be clinically relevant. Dentists may assess how the teeth contact as part of a broader examination, particularly when there are missing teeth, restorative changes, or functional difficulties.

But bite findings should be interpreted alongside the joints, muscles, symptoms, and movement pattern rather than assumed to be the root cause of clicking.

Acute Jaw Injury: The Macro-Trauma Pathway

Unlike many proposed risk factors, direct trauma to the jaw or temporomandibular joint can contribute to some TMDs.

Examples may include:

• A direct blow to the jaw or face
• Jaw fracture or dislocation
• Sports-related facial trauma
• Other injuries involving substantial force to the jaw

Trauma can affect the joint capsule, ligaments, disc, bone, and surrounding muscles. The resulting effects depend on the direction and severity of the injury.

Whiplash has also been associated with TMD symptoms in some studies. However, research has not established a simple or universal cause-and-effect pathway between whiplash and TMJ disc displacement.

Can keeping the mouth open too long cause a problem?

Prolonged or forceful mouth opening can temporarily strain the jaw in some people.

Dental procedures, intubation, or other procedures requiring sustained wide opening have been reported as triggers for TMJ dislocation, particularly in susceptible individuals. They may also aggravate pre-existing jaw symptoms.

However, evidence is not strong enough to state that prolonged dental treatment commonly causes permanent ligament damage or anterior disc displacement.

A history of prior locking, dislocation, trauma, or significant TMD symptoms may therefore be relevant before procedures that require extended mouth opening.

Joint anatomy and tissue characteristics also matter

Not every person experiences the same mechanical environment within the TMJ. Additional factors may influence disc position or joint behaviour, including:

• Joint hypermobility or capsular laxity
• Changes in disc shape or mechanical properties
• Variations in joint anatomy
• Altered lubrication within the joint
• Degenerative joint changes
• Previous trauma

These factors may interact rather than operate independently.

The most accurate model is therefore multifactorial: jaw clicking and disc displacement can develop through different combinations of mechanical, anatomical, muscular, and biological influences, and in many cases no single cause can be identified.

Wilkes Classification of Internal TMJ Derangement

Jaw clicking is sometimes discussed as part of internal derangement, meaning an altered structural or functional relationship between the articular disc, mandibular condyle, and other structures within the temporomandibular joint.

One historical framework used to describe the severity of these internal changes is the Wilkes staging system. It divides TMJ internal derangement into five stages based on combinations of symptoms, disc position and shape, joint function, and structural findings.

The stages are useful for describing increasingly extensive joint changes, but they should not be interpreted as a prediction that a painless clicking joint will inevitably progress through every stage.

Modern TMD diagnosis also uses more specific categories, such as disc displacement with reduction, disc displacement with intermittent locking, disc displacement without reduction, and degenerative joint disease.

Stage I: Early Disc Displacement

Typical pattern: Painless or minimally symptomatic clicking

In the original Wilkes framework, the earliest stage involves relatively minor displacement of the articular disc while its overall shape remains largely preserved.

A person may experience:

• Light clicking during opening or closing
• Little or no pain
• Normal or near-normal mouth opening
• No significant limitation in jaw function

Imaging may show slight anterior displacement of the disc without significant bony changes. This stage illustrates an important point: disc displacement can exist without pain or disability. Many people with disc displacement with reduction remain stable and symptom-free for years, so the presence of an early click does not by itself establish progressive joint disease.

Stage II: Early to Intermediate Internal Derangement

Typical pattern: More noticeable clicking with intermittent symptoms

At this stage, the disc may remain displaced but begin to show early changes in shape. Symptoms described within the Wilkes framework can include:

• More pronounced clicking
• Occasional joint tenderness or pain
• Intermittent catching or brief locking
• Periodic discomfort during chewing
• Generally preserved jaw opening between episodes

The click may occur later during the opening movement as the condyle-disc relationship changes.

Importantly, symptoms can fluctuate. Someone who experiences intermittent pain or locking does not necessarily continue toward more advanced structural disease.

Stage III: Intermediate Internal Derangement

Typical pattern: Disc displacement may stop reducing consistently.

In the original Wilkes framework, Stage III represents more advanced internal derangement, with greater disc displacement and deformation and variable clinical and imaging findings.

At this stage, some patients may develop disc displacement without reduction, meaning the displaced disc no longer consistently returns to its previous relationship with the condyle during opening.

Possible features include:

• Recurrent episodes of joint pain
• Catching or locking
• Reduced mouth-opening range
• Difficulty chewing during symptomatic periods
• Deviation of the jaw toward the affected side in some cases

When disc displacement without reduction produces restricted opening, the clinical presentation is commonly called a closed lock.

A person may sometimes notice that a joint which previously clicked no longer does so, while mouth opening becomes restricted.

However, the disappearance of a click does not automatically mean that the condition has progressed to a closed lock.

Clinical examination is needed to determine why the sound changed.

Stage IV: Intermediate to Late Structural Change

Typical pattern: Chronic internal derangement with early or moderate degenerative changes

The original Wilkes classification describes Stage IV as involving more advanced disc deformation together with early to moderate changes in the bony joint surfaces.

• Symptoms can vary and may include:
• Episodic or chronic joint pain
• Restricted jaw movement
• Stiffness
• Functional difficulty
• Changes in joint sounds

Importantly, structural change and pain do not always correlate closely. A person can have imaging abnormalities with limited symptoms, while another person can experience considerable pain without severe structural findings.

Stage IV therefore should not be diagnosed from symptoms alone.

Stage V: Late Internal Derangement and Advanced Degenerative Change

Typical pattern: Extensive disc and joint-surface abnormalities

Stage V is the most structurally advanced category in the Wilkes system. Imaging or surgical findings may include:

• Marked disc deformation
• Persistent non-reducing disc displacement
• Possible disc or posterior attachment perforation
• More extensive degenerative changes to the mandibular condyle or other joint surfaces

Patients may experience pain, restriction, functional difficulty, or coarse joint sounds such as crepitus, although symptoms vary substantially.

It would be inaccurate to describe this stage simply as “raw bone rubbing against the skull.” Degenerative TMJ disease involves changes in cartilage, subchondral bone, joint shape, and other tissues, and the process is more complex than direct bone-on-bone friction.

Does a clicking jaw normally progress through these stages?

No.

The original Wilkes model described internal derangement as a potentially progressive process. Later research has shown that the natural history is far less predictable.

Disc displacement with reduction is often:

• Painless
• Stable over time
• Compatible with normal jaw function
• Does not inevitably progress to symptomatic disc displacement without reduction or persistent locking

A systematic review found that disc displacement with reduction is generally a stable, pain-free condition and that only a small minority of discs lose their ability to reduce during opening.

Even disc displacement without reduction does not always remain severely symptomatic. Pain and restricted opening can improve over time in many patients.

For this reason, the Wilkes system is best used as a descriptive framework for increasing structural severity, not as a timeline showing what will happen to every patient with a clicking jaw.

How Modern Diagnosis Differs From Wilkes Staging

Contemporary TMD assessment often uses the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) rather than assigning every patient a Wilkes stage.

Clinicians may distinguish among conditions such as:

• Disc displacement with reduction
• Disc displacement with reduction with intermittent locking
• Disc displacement without reduction with limited opening
• Disc displacement without reduction without limited opening
• Degenerative joint disease
• Subluxation

This approach helps separate different joint disorders rather than assuming they are sequential phases of one disease.

Symptoms such as painful clicking, repeated locking, persistent restriction in mouth opening, or significant changes in jaw function are therefore more useful reasons for assessment than trying to determine a Wilkes stage from the sound of the joint alone.

Clinical Triage: When does jaw clicking need evaluation?

A jaw click by itself is not enough to determine that something is wrong with the temporomandibular joint. Painless clicking or popping with normal jaw movement is common, and current clinical guidance generally does not recommend treatment for the sound alone.

The picture changes when clicking occurs with pain, catching, locking, restricted movement, or a noticeable change in jaw function. These additional findings provide more useful information than the volume or frequency of the sound by itself.

Painless Clicking With Normal Movement

If the jaw clicks but does not hurt, lock, or restrict opening, the sound alone generally does not require active treatment.

This is particularly important because attempting to eliminate an asymptomatic click can lead to unnecessary intervention. Painless TMJ clicking and popping are common and generally do not require treatment.

Monitoring is more appropriate. Pay attention to changes in comfort and function rather than repeatedly testing the joint or trying to make it click.

Clicking With Pain

A click becomes more clinically relevant when it occurs alongside pain in the jaw joint or chewing muscles.

Pain may be felt directly in front of the ear or may involve the jaw, face, temple, or nearby muscles. However, these symptoms are not specific to disc displacement, and pain around the face or jaw can have causes unrelated to TMD.

A clinician may therefore evaluate the location and behaviour of the pain, jaw movement, muscle tenderness, joint sounds, and other findings before determining which TMD category, if any, best explains the symptoms.

Catching, Locking, or Reduced Opening

A jaw that catches or temporarily locks deserves more attention than clicking alone. Disc displacement can sometimes interfere with normal condylar translation. When the disc intermittently prevents movement before reducing, the person may describe a brief catch or hitch during opening.

If the disc no longer reduces, mouth opening can become restricted. Under modern diagnostic terminology, this can be classified as disc displacement without reduction with limited opening when the relevant diagnostic criteria are met.

Importantly, limited opening can also result from muscle disorders, inflammation, trauma, infection, and other conditions. A patient should not assume that a restricted jaw automatically means the disc has become permanently displaced.

What If the Clicking Suddenly Stops?

The disappearance of a click is not automatically good or bad. In some people, a click may simply become less noticeable or disappear without producing functional problems.

In others, a history of clicking followed by a sudden reduction in mouth-opening range can be consistent with a transition from a reducing to a non-reducing disc displacement, sometimes described clinically as a closed lock.

The key distinction is therefore:

Click disappears + jaw moves normally:

Not necessarily concerning.

Click disappears + opening becomes restricted or the jaw locks:

Professional evaluation is appropriate.

The change in function is more meaningful than the disappearance of the sound itself.

How much mouth opening is considered restricted?

There is no useful reason for patients to repeatedly measure their own jaw opening at home.

Clinically, the DC/TMD system evaluates maximum unassisted and assisted mouth opening as part of assessing suspected disc displacement without reduction. In the DC/TMD examination protocol, maximum assisted opening is measured as part of the assessment of suspected disc displacement without reduction with limited opening. A value below 40 mm, measured according to the protocol, is one component of the diagnostic criteria rather than a stand-alone definition of restricted opening.

That number should not be used as a stand-alone home diagnostic test. Jaw size, pain, muscle guarding, previous range of motion, and examination findings all matter.

When a Jaw Stuck Open Is Different From a Closed Lock

The phrase “jaw locking” can describe two very different situations.

A closed lock generally refers to restricted opening, commonly associated with disc displacement without reduction.

A jaw that becomes stuck in a wide-open position and cannot close raises a different concern: mandibular dislocation. In an anterior dislocation, the mandibular condyle moves beyond the articular eminence and cannot readily return to its normal position.

This is an urgent problem that requires prompt professional management. Patients should not attempt forceful self-reduction.

The Most Useful Rule: Track Function, Not Noise

For jaw clicking, the most clinically useful questions are:

Does it hurt? Does the jaw catch or lock? Has mouth opening changed? Is chewing becoming difficult? Have the symptoms changed significantly over time?

A painless click with unrestricted function may remain stable without treatment. Painful clicking, recurrent locking, persistent movement restriction, or a substantial change from the person’s usual jaw function provides a stronger reason for clinical assessment.

This type of symptom-based triage is useful for deciding when an evaluation may be appropriate, but it cannot identify the exact position of the TMJ disc or assign a diagnosis without a clinical examination.

How is a clicking jaw treated?

Treatment depends on whether the clicking is painless or occurs with pain, locking, restricted movement, or other functional problems. Painless clicking with normal jaw function generally does not require treatment simply to eliminate the sound. When symptoms are present, management typically begins with conservative and reversible approaches rather than procedures that permanently alter the teeth, bite, or joint.

Self-Management and Activity Modification

Early management may include temporarily reducing activities that aggravate symptoms, avoiding very wide or forceful jaw movements, and limiting habits such as gum chewing or jaw clenching. Heat or cold and gentle jaw exercises may also be recommended depending on the symptoms and clinical findings.

The goal is to reduce discomfort and maintain comfortable jaw movement rather than repeatedly testing the joint or trying to force the click to disappear.

Physical Therapy and Behavioural Strategies

Physical therapy may be used to improve jaw movement and function and address contributing muscle symptoms. Behavioural approaches can also help patients recognize and reduce habits such as jaw clenching or bracing.

Stress-management strategies may be useful when stress increases muscle tension or parafunctional habits, but this should not be interpreted to mean that stress is necessarily the underlying cause of the joint clicking.

Occlusal Splints and Night Guards

A dentist may consider a reversible occlusal splint or custom-milled stabilization splint for selected patients, particularly when clenching or grinding, tooth wear, or muscle symptoms are part of the clinical picture.

Splints may help protect the teeth or reduce symptoms in some patients, but they do not reliably eliminate clicking, permanently reposition a displaced disc, or cure TMD. An appliance should not be designed to permanently change the bite.

When More Investigation or Referral May Be Appropriate

Persistent pain, recurrent locking, significant restriction in mouth opening, symptoms following trauma, or other concerning findings may warrant further investigation or referral. Imaging may be considered when it would meaningfully affect diagnosis or management; MRI is particularly useful when assessment of the TMJ disc and other soft tissues is required.

More invasive procedures are generally not the first approach for uncomplicated jaw clicking or TMD symptoms. Treatment decisions should be based on the specific diagnosis, severity of symptoms, functional limitations, and response to conservative care.

Conclusion

Jaw clicking is often more about how the temporomandibular joint is moving than about the sound itself. In many cases, painless clicking can remain stable without treatment, while pain, locking, restricted opening, or changes in normal jaw function provide stronger reasons for professional evaluation.

The most important step is avoiding assumptions based on the click alone. Disc displacement, muscle-related symptoms, trauma, and other joint conditions can produce overlapping signs, which is why diagnosis depends on the overall pattern of symptoms and clinical findings.

At Yaletown Dental Boutique, TMJ assessment can focus on jaw movement, muscle and joint symptoms, bite function, and other relevant findings to help determine when monitoring or conservative management may be appropriate. The goal is not necessarily to create a completely silent joint, but to support comfortable, functional jaw movement and identify changes that may need further attention.