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What is Trismus (LockJaw), its Causes, Symptoms, Diagnosis and Treatment?

Trismus, it is also known as the locked jaw. This signifies the reduced or restricted opening of the jaw. Normally, the mouth opening is 35mm– 45mm (up to 3 fingers wide), males have slightly greater mouth opening(40mm– 60mm). When the mouth opening occurs less than 30mm, the condition is considered as trismus or locked jaw.

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Initially, the occurrence of locked jaw disease can be noticed in the form of clicking and popping sound of the jaw while opening or closing of the mouth, the frequent occurrence of pain in relation to the joint of the jaw (TMJ or temporomandibular joint), this is present in front of the earlobe. So these initial symptoms must be taken care and consultation to your dentist must be done if any of these are noticed.

Now, let’s see the actual causes in relation to the locked jaw

Causes of Trismus

There are several causes which can lead to the lockjaw these causes can be

Causes of trismus


The infection in relation to the temporomandibular joint area (ie, the joint at front of the ear lobe which allows the opening and closing of the mouth). The infections can be pericoronitis (occurs mostly in relation to the wisdom tooth), Ludwig’s angina, submassetric or infratemporal abscess.

Trismus for TMJ


Any kind of trauma such as a fracture to the zygomatic arch (cheekbones) causes restricted jaw opening. Also, the fracture of the mandible can cause the locked jaw, due to the pain, tenderness and muscle spasm.


There are various habits such as involuntary grinding and clenching of teeth (bruxism) which causes excessive pressure over the muscles of the joint which causes pain and tenderness which leads to the restricted opening of the jaw.


Myositis that is inflammation of muscles or the muscular atrophy can cause the locked jaw. Due to the inflammation, the movement of the jaw becomes restricted and painful, which causes the decreased opening of the jaw.

Teeth Related Problem

Sometimes the misalignment of the teeth causes imbalanced occlusion due to which, the mouth cannot be closed properly this causes constant pressure over the jaw joint area which leads to the painful swelling.

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It is the infection which is caused by the Clostridium tetani, in this, the typical symptom is persistent tonic muscle spasm (involuntary muscle contraction) which leads to severe pain and decreased the opening of the jaw.

Neurological Disorder

Several neurological disorders like epilepsy, brain tumor, bulbar paralysis, embolic hemorrhage medulla oblongata can also cause the trismus.

Psychosomatic Trismus

Due to various psychological factors like fear, anxiety, and stress, which increases to such a level that it can cause hysterical fits can also trigger the occurrence of the decreased opening of the mouth.

Mechanical Blockage

Any kind of mechanical blockage in the pathway of opening or closing of mouth causes the trismus. The blockage could be due to the Elongation of the bone in relation to the TMJ, exostosis(ie, a benign outgrowth of the cartilage in relation to bone), osteoma, osteochondroma of the coronoid process will cause the mechanical blockage and interfere with the normal mandibular movements.

Extra-Articular Fibrosis

In this, the cause of the fibrosis is not in relation to the joint but the surrounding tissue. Chronic cervicofacial sepsis, post radiation therapy, ossification of the sphenomandibular ligament, bands of scars, burns in relation to the face and neck region, oral submucous fibrosis will lead to trismus.

Symptoms of Locked Jaw

Symptoms of trismus



  • Severe pain in the jaw joint area
  • Pain while opening or closing of the jaw
  • Clicking and popping sounds while movement of the mouth
  • Increased muscle tiredness
  • Pain while chewing food
  • Swelling of the sides of the face
  • Headache
  • Earache
  • Dizziness

Diagnosis of Trismus

Firstly the symptoms in relation to TMJ disorders, such as the pain, clicking and popping sound, inability to open mouth, inability to close mouth, swelling and tenderness related to joint are seen and are indicative of TMJ problems, for further diagnosis there are several tests like

OPG (Orthopantomogram)


It is full face x-ray, this allows the dentist to detect any abnormality in any side of the temporomandibular joint.

MRI and CT Scan

MRI allows seeing if the TMJ disc is at the proper position, which allows the easy function of the joint. CT Scan allows seeing the bony details in relation to the temporomandibular joint.

Treatment of the locked Jaw

Manual Realignment of the Jaw

It is done in the case when the person comes to the clinic with the jaw stuck at one position, this can be a very painful situation. In this, the dentist manually realigns the joint, this is done by placing thumb or index finger on teeth of either side of the lower jaw, then just push the jaw at downward and then backward position, then will realign at its normal position. This is the technique sensitive procedure and must be done with the right technique.


Analgesic– Firstly your dentist will provide pain-relieving medicines which will help to decrease pain.

Muscle Relaxants– Due to excessive pressure over the muscles of joints, the pain can increase, this increases the chances of TMJ related disorders such as lockjaw, so muscle relaxants are given to decrease the tenderness in the muscles.

Antianxiety Medication– The TMJ related disorder which is occurring due to the increased emotional imbalance, is relieved by the antianxiety medicines, but for the long term cure along with this, the person should increase the stress relieving exercises like yoga and meditation.

Splint or Night Guard

There is various kind of appliances which are used to guide the patient to overcome the habits which cause excessive pressure and damage to the joint of the jaw, these are splints or the mouthguards. Mouth guards are mouthpieces that are used while sleeping, to reduce the chances of involuntary grinding or clenching of the teeth, which otherwise cause excessive pressure over the jaw joint and lead to the problem of lockjaw.

Teeth Related Problem

If there is any kind of malocclusion or the imbalance in the occlusion of teeth, it will also cause the overpressure on the jaw joint leading to the pain and trismus. These problems must be corrected by the dentists for better occlusal balance.

TENS (Transcutaneous Electrical Nerve Stimulation)

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In this, the low level of electrical current is used to provide the relaxation of the muscles and to relieve the tenderness or pain of the muscles. This procedure is done by specific instruments, this relieves stress in the muscles and allow it to function normally.

Ultra Sound– In this, the deep heat therapy is given by the ultrasound waves, this relaxes the muscles and relieves stress and pain from it.

Trigger Point Injections

In this, the anesthetic agent or the pain relieving agent is injected inside the muscles to give immediate relief to the pain. These are used when the manual relocation of the TMJ is not possible and the pain is not bearable by the patient.

Radio Wave Therapy

For several muscle spasms, radio wave therapy is also considered effective, as they help to increase the blood flow of the area and are useful for easing the pain.

Surgical Approach

If the conservative treatments do not help the patient for relieving the joint related problems which further leads to the trismus and lockjaw, then there are surgical approaches to be considered useful.

  • Arthrocentesis–Β It is a safe and minimally invasive technique, in this the joint is washed off by the saline or ringer lactate solution. This will help to remove all the deposits surrounding the joint and also calm down the inflamed tissue, at last, the steroid is injected to relieve the muscle stress and restore the normal function of the joint. The procedure can be done under local anesthesia in which only the tissue surrounding the jaw joint is numbed or it can also be done under general anesthesia in which person is made unconscious or put to sleep before the procedure done.
  • Arthroscopy–Β This is the procedure in which the arthroscope is used for examining the jaw joint. The arthroscope is a tool consist lens and light on it, it is inserted in the joint area through a small cut and the inner picture of the joint can be seen on the screen. This is very helpful to examine the joint and to solve the exact issue ie, the surgeon can remove the inflamed tissue and also can realign the disc in relation to jaw joint. This is done under the general anesthesia.
  • Open Joint Surgery– This is done when the bony structures are misaligned, any tumor present around the joint, joint is scared, bone is displaced, etc. In this, the joint area is completely opened and the proper realignment of the joint is done. This is done under general anesthesia and also the healing takes longer than the above-discussed techniques.

Home Remedies for Lock Jaw

Hot and Cold Compress

The person can use hot compress for 10 to 15 minutes twice a day to relieve the muscle stiffness, relax muscles, increase the blood supply in muscles. If the hot compress doesn’t relieve the pain then the person can use cold compress which will reduce swelling, decrease muscle stress and relieves pain.

Jaw Movement and Exercise

Jaw exercise

Jaw exercises like opening and closing of mouth several times, then sideways movements of jaw and massage of the muscles surrounding the jaw joint for 15 to 20 minutes twice a day are effective home remedies for relieving the TMJ problem. But if the problem increases with time, and the pain and discomfort is not relieved in one or two days then the person must visit there dentist for a proper examination.

This was all about the lockjaw or trismus, hopefully, this was helpful to provide you a little glance about the topic, for any specific detailed explanation or any questions you can write us in the comment section below.

Deepak Kansal

Deepak Kansal

I am a Dental Professional, Acquainted Content writer and creator, Imparting valuable dental knowledge through and working towards making a difference. Any information provided on the Trickycare platform is for general information only and does not constitute professional advice.

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