Trismus, often called "lockjaw", is the limited opening or hypomobility of the mouth, i.e. where you have a restricted and limited range-of-motion of the mouth. Trismus has a variety of causes, and can occur from nerve, muscle, or joint problems. Trismus or lockjaw is an early symptom of tetanus, but is most frequently caused by radition to the face, jaw, mouth or nose for cancer therapy.  Trismus is also often associated with difficulty swallowing (dysphagia).

Definition:  Any restriction in mouth opening, often caused by infection, trauma, surgery, or radiation
Synonyms: Jaw hypomobility, restricted opening, limited range-of-motion (ROM), lockjaw
Measurements: MIO/D - Maximum Intercisal Opening/Distance; or  ROM - Range-of-Motion

Normal MIO:      Men 50-60mm Women 45-55mm
Trismus:    Decreased function of less than 30-35mm MIO.
Basic Diagnostic - The 3-Finger Test:                          
    Insert Tips of index, middle and ring fingers non-dominant hand between front teeth.

Normal Oral Opening
>40 mm
3+ Fingers
Mild Trismus
30-40 mm  
2-3 Fingers
Moderate Trismus
15-30 mm 
1-2 Fingers
Severe Trismus
<15 mm
<1 Finger
The negative of effects of trismus include difficulty speaking, eating, drinking, coughing, sneezing, and maintaining oral hygiene. These are serious quality of life issues that require significant attention, and overlooking them can lead to malnutrition, dehydration, social disorders, addiction, and muscle/joint degeneration.

Common causes of trismus include: TMJD, burn scars, radiation treatment to the jaw and head, arthritis, scleroderma, fibromyalgia, trauma, infection, impacted wisdom teeth, psychological conditions including stress, bruxism and grinding, congenital conditions, and other muscluloskeletal conditions.

Trismus can occur as a chronic long-term symptom of a broader condition, like arthritis or scleroderma, or as a unique and reversible condition. Treatments are generally the same, however chronic sufferers will need to maintain treatment for continued relief.

Unfortunately, the lack of motion from trismus can allow the joint to degrade, making movement even harder. Treating trismus early can prevent severe joint damage, and provide significantly improved quality of life. Degeneration of joint tissue has been shown in as little at 3 days of joint immobilization, with thinning cartilage and increasing viscosity of the synovial fluid.

Treatment options include:
Oral Cancer Foundation - Trismus Information
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