Veterinary Guide to Lockjaw (Trismus) in Dogs 2025 🐶🩺

By Dr. Duncan Houston BVSc

🧬 What Is Lockjaw (Trismus)?

“Lockjaw,” medically known as trismus, occurs when the masticatory muscles spasm, causing dogs to be unable—fully or partially—to open their mouths. While historically linked to tetanus, many other causes exist.

👥 Who’s Affected?

• Adult dogs are most commonly affected.
• No strict breed predilection, though certain breeds—German Shepherds, Labs, Goldens, Dobermans, Cavaliers—are more prone to masticatory muscle myositis (MMM).

⚠️ Primary Causes of Trismus

1. Tetanus: Clostridium tetani infection from deep puncture wounds; causes rigid jaw closure and muscle spasms.
2. Masticatory Muscle Myositis (MMM): autoimmune inflammation targeting jaw muscles; acute swelling or chronic atrophy leading to fibrosis and lockjaw.
3. Temporomandibular Joint (TMJ) Disorders: arthritis, luxation, ankylosis, fractures—cause mechanical jaw restrictions.
4. Trauma & Surgical Injuries: fractures, abscesses, nerve damage—all can induce trismus.
5. Neurologic & Neoplastic Causes: nerve paralysis, brain/spinal tumors may impair jaw control.
6. Dental or Retrobulbar Infections: Abscesses can inflame muscles and limit jaw motion.

⚠️ Clinical Signs

• Inability or difficulty in opening/closing mouth.
• Painful chewing, dropping food, and vocal distress.
• Excessive drooling, salivation, inflamed or swollen jaw.
• Visible third eyelid, eye swelling, exophthalmos with MMM.
• Fever (common in tetanus, abscesses).
• Visible muscle atrophy in chronic MMM.

🔍 Diagnostic Approach

1. History & Physical Exam: note wounds, vaccination history, dental issues, behavioural change.
2. Bloodwork: CBC, chemistry; note infection, inflammatory markers, muscle enzymes (CK) for MMM.
3. MMM-specific Testing: 2M antibody ELISA and muscle biopsy confirm diagnosis.
4. Imaging (X-rays, CT): assess TMJ, fractures, abscesses.
5. Neurologic Assessment: evaluate for nerve or brain-related causes.

🛠️ Treatment Options

1. Tetanus Management

• Clean wound, administer tetanus antitoxin or immunoglobulin.
• Initiate antibiotics (penicillin) and muscle relaxants (diazepam).
• Provide supportive care: IV fluids, nutrition via feeding tubes, thermal support.

2. MMM Therapy

• Begin high-dose corticosteroids (prednisone); taper gradually.
• Use manual jaw stretching under anesthesia to reduce fibrosis.
• Maintain soft or liquid diet during recovery.

3. TMJ & Trauma Care

• Fracture repair, joint stabilization, or arthroplasty for TMJ issues.
• Extract foreign objects, drain abscesses, treat underlying conditions.

4. Neurologic/Oncologic Intervention

• Treat underlying tumors or nerve lesions as indicated.
• Symptomatic care—anti-inflammatories, nutrition, physical therapy.

5. Supportive & Physical Rehabilitation

• Pain control: NSAIDs, opioids, muscle relaxants.
• Physiotherapy to maintain jaw mobility.
• Nutrition management—wet food, feeding tubes if needed.

📈 Prognosis

• Tetanus: Guarded; favorable if treated early; prolonged recovery with supportive care.
• MMM: Good with early immunosuppression and stretching; chronic cases may have residual stiffness.
• TMJ/Trauma: Anatomical repair often yields a good outcome; ankylosis or central lesions have poorer prognosis.

📱 Ask A Vet Telehealth Integration

• 📸 Upload wound/jaw exam & imaging for specialist review.
• 🔔 Medication reminders for antibiotics, steroids, relaxants, and physiotherapy.
• 🩺 Virtual check-ins to assess jaw mobility, pain, eating, and signs of improvement.

🎓 Case Spotlight: “Max” the German Shepherd

Max presented with sudden difficulty opening his mouth, fever, and jaw swelling. Bloodwork showed high CK, elevated antibodies for MMM. Treatment: high-dose steroids, manual stretching under anesthesia, soft diet. Ask A Vet coordinated lab monitoring, taper reminders, and delivered supportive supplements. Within 6 weeks Max regained near-normal jaw function and returned to chewing kibble 🐾.

🔚 Key Takeaways

1. Trismus (lockjaw) is a nonspecific sign of various serious conditions including tetanus, MMM, TMJ disease, trauma, and neurologic disorders.
2. Causes are diverse—accurate diagnosis using history, bloodwork, imaging, and specific tests is critical.
3. Treatment depends on the underlying cause: antitoxin & antibiotics for tetanus; steroids & stretching for MMM; surgery for TMJ/trauma.
4. Outcome is best with early intervention—delays may lead to fibrosis or permanent disability.
5. Ask A Vet telehealth enhances care through remote diagnosis, treatment coordination, physical therapy guidance, medication delivery, and recovery monitoring 📲🐕

Dr Duncan Houston BVSc, founder of Ask A Vet. Download the Ask A Vet app to support your dog with lockjaw—offering remote evaluation, medication coordination, physiotherapy plans, feeding support, and quality-of-life monitoring 🐶📲