Jaw pain when you open your mouth is most commonly caused by a problem with the temporomandibular joint (TMJ), the hinge that connects your lower jaw to your skull, or with the muscles that control chewing. About 5% of U.S. adults experience these issues, collectively called temporomandibular disorders (TMDs), and they’re at least twice as common in women as in men. The pain can range from a dull ache to a sharp catch that stops you mid-bite, and the cause determines what you should do about it.
Muscle Tension and Trigger Points
The most common reason your jaw hurts when you open wide is muscle tension, fatigue, or spasm in the muscles you use to chew. These are powerful muscles that run along the sides of your face and skull, and when they’re overworked or chronically tight, they develop tender spots called trigger points. Those trigger points don’t just hurt where they are. They send pain radiating to other parts of your face, head, and jaw, which is why the discomfort can feel diffuse and hard to pinpoint.
Muscle-driven jaw pain typically limits how far you can open your mouth, and your jaw may drift toward the painful side as you open. Unlike joint problems, this deviation tends to be somewhat inconsistent rather than catching at the exact same point every time. The pain is often worst in the morning if you’ve been clenching or grinding overnight, or in the evening after a stressful day of unconscious jaw tension. A restricted opening below about 40 millimeters (roughly the width of three fingers stacked between your front teeth) is a common clinical marker for a muscular problem.
A Displaced Disc in the Joint
Your TMJ contains a small cartilage disc that acts as a cushion between the bones. When this disc slips out of position, it changes how the joint moves, and you’ll often hear or feel the result.
In the more common version, called disc displacement with reduction, the disc slips forward when your mouth is closed. As you open past about 10 millimeters, the disc pops back into place with an audible click. You may hear a second, quieter click when you close as the disc slips forward again. This clicking is often painless on its own, but chewing tough or chewy foods can aggravate the surrounding tissues and cause real discomfort.
The more concerning version is disc displacement without reduction, sometimes called a “closed lock.” Here the disc stays stuck out of position and physically blocks your jaw from opening fully. This causes a sudden, noticeable restriction in how far your mouth can open, along with pain around the joint and ear. If your jaw suddenly won’t open more than a finger-width or two, this is likely what’s happening.
Both types can inflame the capsule of ligaments and connective tissue around the joint. That inflammation alone produces localized pain, tenderness when you press on the joint, and sometimes further restriction in opening.
Teeth Grinding and Sleep Problems
Bruxism, the habit of clenching or grinding your teeth, is one of the biggest contributors to jaw pain. Many people do it in their sleep without realizing it. The forces involved are significant, sometimes exceeding what you’d generate during normal chewing, and hours of sustained clenching exhausts the jaw muscles and strains the joint.
There’s an interesting connection between teeth grinding and obstructive sleep apnea. One theory is that when your airway narrows during sleep, the grinding motion helps reopen it, essentially making bruxism an unconscious protective reflex. Another is that clenching helps lubricate throat tissues that dry out from labored breathing. If you wake up with a sore jaw and your partner has noticed you snore heavily, the two problems may be linked. Treating the breathing issue sometimes reduces the grinding.
Less Common Causes
Not all jaw pain traces back to the TMJ or chewing muscles. A salivary gland stone can block one of the ducts near your jaw, causing swelling and pain that worsens when you eat (since eating triggers saliva production). Ear infections can radiate pain forward into the jaw area. A condition called first bite syndrome causes sharp pain near the lower jaw or the parotid gland (just in front of your ear) when you start eating, then fades as you continue. It’s typically related to nerve damage from a tumor or surgery in the head and neck area.
Direct trauma to the jaw, even something you don’t think of as a major injury, can damage the joint or surrounding tissues. In rare cases, infection or injury can cause the joint to fuse (a condition called ankylosis), making it increasingly difficult to open your mouth at all.
Who Gets TMD
TMD peaks in younger adults, which is unusual for a chronic pain condition. Based on national survey data, prevalence is highest in the 35 to 54 age range, hovering around 5%. It’s lower in the youngest adults (about 4.2% among 18 to 24-year-olds) and drops to 3.7% by ages 65 to 74. Women are affected roughly twice as often as men: 6.2% versus 3.2%. The reasons for this gender gap aren’t fully settled, but hormonal differences, differences in pain processing, and higher rates of certain contributing conditions all play a role.
What You Can Do at Home
Most jaw pain from muscle tension or mild disc issues improves with conservative care. A simple self-mobilization technique involves placing your index finger on your lower front teeth and your thumb on your upper teeth, then gently applying a spreading pressure to encourage the jaw to open further. Hold the stretch at your maximum comfortable opening for about 10 seconds, and repeat five to six times. Do this routine three times a day for about 10 minutes, working toward being able to fit three fingers between your front teeth. If the stretching causes pain afterward, apply an ice pack to the area.
Beyond stretching, a few habits make a meaningful difference. Avoid chewing gum, biting your nails, or eating very hard or chewy foods while you’re symptomatic. Try to catch yourself clenching during the day. Keep your teeth slightly apart with your tongue resting on the roof of your mouth as a default resting position. Warm compresses before stretching and cold packs after can help manage inflammation.
Splints and Professional Treatment
If home care isn’t enough, a stabilization splint (a custom-fitted mouthguard, usually worn at night) is one of the most studied treatments. A network meta-analysis of randomized trials found that for joint-related TMD, a specific type of repositioning splint ranked highest for pain reduction, while for muscle-related TMD, smaller anterior splints performed best. Standard hard stabilization splints also showed meaningful benefit for both types. Custom splints made by a dentist consistently outperform generic drugstore guards because they’re designed to distribute bite forces evenly across your specific jaw alignment.
For a locked jaw where the disc won’t return to position, a minimally invasive procedure called arthrocentesis, essentially flushing the joint with fluid, has been shown to reduce pain and improve opening. Physical therapy focused on the jaw, including manual joint mobilization and targeted exercises, is another effective option that works well alongside splint therapy.
One important note from the research: despite persistent belief, a “bad bite” or history of orthodontic braces does not cause TMD. Pursuing aggressive treatments to correct your bite alignment as a fix for jaw pain is not supported by current evidence.
Signs That Need Prompt Attention
Most jaw pain resolves or becomes manageable within weeks of conservative treatment. But certain situations warrant faster action. If your jaw suddenly locks and you can’t open it more than a finger-width, if you develop a fever along with jaw pain and swelling (suggesting possible infection), if pain appeared after a blow to the face or accident, or if you notice numbness or tingling in your face alongside the pain, these are situations where waiting and stretching at home isn’t the right approach. A dentist experienced with TMD or an oral and maxillofacial specialist can evaluate whether imaging or a more targeted intervention is needed.