Have you ever heard of a condition where a person cannot open their mouth properly — as if their jaw is “locked”? This is known as lockjaw, medically called trismus. While many associate it with tetanus, a serious bacterial infection, lockjaw can also arise from dental, muscular, or neurological causes.

In this blog, nellikka.life explores the science, causes, symptoms, and treatment of lockjaw — separating myths from facts and highlighting how early care can make a crucial difference.

What Exactly Is Lockjaw (Trismus)?

Trismus is a medical term for restricted mouth opening, typically less than 35 millimeters between the upper and lower front teeth. The term “lockjaw” became popular because tetanus, caused by Clostridium tetani, classically leads to this symptom due to severe muscle spasms in the jaw and neck.

However, trismus can also occur without tetanus, and understanding the underlying cause is essential for proper treatment.

The Classic Cause: Tetanus Infection

What is Tetanus?

Tetanus is a potentially fatal disease caused by the neurotoxin tetanospasmin, produced by Clostridium tetani — a spore-forming bacterium found in soil, dust, and animal feces.
When these spores enter a wound (especially a deep puncture wound), they germinate and release toxins that travel via the nervous system to the spinal cord and brain.

How It Causes Lockjaw

The tetanospasmin toxin interferes with the release of inhibitory neurotransmitters like GABA and glycine, causing continuous stimulation of muscles.
This leads to rigidity and painful muscle spasms, first seen in the jaw muscles (masseter spasm) — hence the name “lockjaw.”

Symptoms of Tetanus-Related Lockjaw

• Inability to open the mouth (trismus)
• Stiff neck and difficulty swallowing
• Painful muscle spasms across the body
• Arching of the back (opisthotonus)
• Fever, sweating, and autonomic instability

Tetanus remains a medical emergency with a high mortality rate if untreated — but it’s entirely preventable through vaccination.

Non-Tetanus Causes of Lockjaw

While tetanus is the most feared cause, many people experience lockjaw due to local or mechanical problems involving the jaw muscles or joints.

Dental & Oral Causes

• Wisdom tooth infection (pericoronitis)
  → Inflammation around the erupting molar can cause muscle spasms in the jaw.
• After dental procedures (like root canal or tooth extraction)
  → Local trauma or prolonged mouth opening can strain the temporomandibular joint (TMJ).
• Oral abscess or cellulitis can cause swelling and pain leading to trismus.

Temporomandibular Joint (TMJ) Disorders

TMJ dysfunction is one of the most common non-infectious causes of lockjaw.
Causes include:

• Jaw injury or arthritis
• Clenching/grinding of teeth (bruxism)
• Stress-induced muscle tightening

Symptoms: clicking sound on opening, pain near the ear, and restricted movement.

Muscle Spasm or Fibrosis

Muscle trauma, repeated injections, or radiation therapy (in head and neck cancers) can lead to fibrosis of the masticatory muscles, causing chronic trismus.

Neurological or Post-Surgical Complications

Certain neurological disorders (like dystonia) or surgeries involving the jaw, neck, or oral cavity can temporarily affect the jaw’s opening mechanism.

Symptoms to Watch For

Depending on the cause, symptoms may include:

• Difficulty or pain while opening the mouth
• Stiffness around the jaw or temples
• Earache or headache
• Difficulty swallowing or chewing
• Facial spasms or tightness
• In severe cases (like tetanus): breathing difficulty and generalized muscle rigidity

Diagnosis

A detailed clinical history and physical examination are key.
Doctors may recommend:

• Blood tests and culture (to rule out infection)
• Imaging (X-ray, MRI, or CT) for TMJ and muscle evaluation
• Electromyography (EMG) if muscle or nerve dysfunction is suspected

For suspected tetanus, diagnosis is clinical, based on muscle stiffness and wound history — no lab test confirms it directly.

Treatment Approaches

1. For Tetanus-Related Lockjaw

• Tetanus Immunoglobulin (TIG): neutralizes circulating toxin
• Antibiotics: usually Metronidazole or Penicillin G
• Muscle relaxants & sedatives: to control spasms
• Mechanical ventilation: in severe cases
• Supportive care and wound cleaning

Vaccination remains the most powerful prevention strategy.

2. For Non-Tetanus Causes

Treatment depends on the cause:

• Warm compresses and gentle jaw exercises for TMJ or muscle spasm
• Anti-inflammatory drugs (NSAIDs) and muscle relaxants for pain relief
• Antibiotics for dental or soft-tissue infections
• Physical therapy and jaw-stretching devices for post-radiation fibrosis
• Stress management if bruxism or muscle tension is a factor

Prevention

For Tetanus:

• Keep tetanus vaccination (TT or Td booster) up to date every 10 years.
• Clean wounds immediately and seek medical help for deep cuts.
• Never ignore a rusty-metal injury or soil-contaminated wound.

For Non-Tetanus Trismus:

• Maintain oral hygiene and regular dental visits.
• Avoid excessive jaw strain or clenching.
• Use mouth guards if you grind teeth.
• Follow post-surgical care instructions carefully.

When to See a Doctor

Seek urgent medical attention if:

• You suddenly can’t open your mouth
• You have pain or swelling after an injury or dental procedure
• You experience stiffness, fever, or muscle spasms spreading to other areas

Early diagnosis helps prevent complications like airway obstruction, malnutrition, and in tetanus cases, even death.

Lockjaw is a reminder that the jaw is not just for chewing — it’s a window into your muscular, neurological, and immune health.
Infections, inflammation, and even stress can “lock” your jaw — but timely medical care, good hygiene, and vaccination can “unlock” your safety.

At nellikka.life, we believe that awareness is the first step to prevention — because even silent conditions can be stopped with informed choices.

References : 
1. Trismus
2. Trismus, the first symptom in a challenging diagnosis of Tetanus
3. What is trismus?
4. Trismus: Aetiology, Differential Diagnosis and Treatment