Based on a Lecture by Dr. Tamara Grubb at Zoomies 2026

Introduction

Chronic pain in animals is an under-recognized and undertreated condition. While animals cannot verbally communicate their pain, they are constantly “telling us” through behavioural changes, mobility alterations, and subtle signals that require careful observation. The mammalian pain pathway is identical across species – what hurts humans also hurts our animal patients. Understanding this is the foundation for recognising and managing chronic pain effectively.

1. Chronic Pain Is a Disease, Not Just Prolonged Acute Pain

Critical distinction: Acute pain serves a protective purpose. It has biological value in helping protect the individual from further injury. Chronic pain, however, is pathologic, non-purposeful, and maladaptive. Unlike acute pain, chronic pain doesn’t resolve with healing; it persists due to abnormal changes in the pain pathway itself. Chronic pain is even present in conditions like phantom limb pain, where pain continues even after the painful body part is removed. Chronic pain represents a malfunction of the pain pathway with no positive return – making it a true disease entity requiring treatment, not merely management.

2. The Pain Pathway Becomes Amplified and Inhibitory Control Fails

In chronic pain states, the nervous system undergoes profound changes:

• Peripheral sensitization: Nociceptors fire spontaneously or to low-level stimuli
• Central sensitization: The spinal cord amplifies pain signals
• Descending inhibition fails: The brain’s ability to “turn down” pain signals becomes dysfunctional

This means patients experience:

• Stimulus-independent pain: Pain even at rest
• Hypersensitivity: Extreme pain from mild stimuli
• Allodynia: Pain from normally non-painful touch (like petting)

These patients hurt all the time and may react aggressively even to gentle handling – not because they are “bad,” but because everything feels painful.

3. Pain Drives Behavioural Changes That Owners Often Misinterpret

Many behavioural problems have undiagnosed pain as their root cause. Across multiple behaviour specialty clinics, 23-82% of referred cases had underlying pain contributing to behavioural issues. Pain-related behavioural changes include:

• Defensive or aggressive behaviour (biting when touched)
• House soiling (litter box avoidance, inappropriate urination)
• Decreased activity and playfulness
• Clinginess or attention-seeking
• Noise sensitivity (especially in older dogs)
• Compulsive behaviours (stargazing, fly snapping)
• Separation anxiety and destructive behaviour
• Fearfulness and anxiety

When behavioural problems appear in mature animals, pain should be high on the diagnostic list, and not be dismissed as “just getting old” or “becoming grumpy.”

4. Cats and Dogs Hide Pain Differently—We Must Teach Owners What to Look For

Owners typically expect pain to look like vocalization, crying, or limping. But animals evolved in a prey-predator world where showing weakness is dangerous. They mask pain for survival. In reality, pain manifests as:

• Mobility changes: Difficulty rising, reluctance to jump or climb stairs, stiffness
• Behaviour changes: Withdrawal, hiding, reduced sociability, decreased grooming
• Loss of joy: Not engaging in previously enjoyed activities

Vocalization and crying are NOT reliable indicators. By the time animals show obvious pain signs, the pain is severe. Teaching owners to recognise subtle changes is essential. Studies show even brief owner education significantly increases recognition of pain signs and likelihood of seeking veterinary care.

5. Pain Assessment Requires Standardised Tools and a Team Approach

Formal pain scoring tools are critical for identifying and monitoring chronic pain. Options include:

• Canine Brief Pain Inventory (musculoskeletal and function)
• COAST (Canine Osteoarthritis Staging Tool)
• Feline Musculoskeletal Pain Index (online tool with owner input)
• Client-Specific Outcome Measures (CSOM): Owners identify specific activities their pet should return to – and  then monitor progress
• Quality of Life Scales: Assess hurt, hunger, hydration, hygiene, happiness, mobility, and good vs. bad days

The entire veterinary team must be involved:

• Veterinarians: Diagnose and prescribe
• Technicians/Nurses: Administer tools and educate
• Front office staff: Listen for owner concerns (“My dog used to be friendly, now he’s grumpy”)
• Owners: Monitor daily changes at home

Pain assessment isn’t optional – it’s essential at every visit and recheck.

6. Untreated Pain Has Widespread Negative Consequences

Pain isn’t just uncomfortable – it actively harms health:

• Cardiovascular effects (hypertension, tachycardia)
• Decreased gastrointestinal motility
• Impaired wound healing
• Stress responses that exacerbate underlying disease
• Behavioural deterioration
• Damaged human-animal bond
• Progressive worsening through central sensitization

Crucial concept: When a patient with chronic pain undergoes a procedure, they require more robust analgesia than a pain-free patient – because the same procedure is NOT the same experience for these patients. Pre-existing maladaptive pain amplifies all new pain stimuli.

7. Treatment Must Be Multimodal and Individualized

Especially when NSAIDs are contraindicated (e.g., in kidney disease), multiple approaches are needed:

• Pharmacologic: Alternative analgesics such as acetaminophen (in dogs), monoclonal antibodies (anti-nerve growth factor), gabapentin etc.
• Joint supplements with scientific backing
• Physical medicine: Rehabilitation, acupuncture, underwater treadmill
• Weight management (critical in drug-limited patients)
• Joint injections
• Nutritional support

Monitoring approach:

• Weekly phone check-ins after starting new therapy
• Monthly rechecks for pain assessment
• Blood work at 4-6 weeks for NSAIDs, then every 6 months depending on age and disease status

Ask the patient with a therapeutic trial: If pain behaviours improve with analgesia, the diagnosis is confirmed. When in doubt, treat—the behavioural specialists support this approach.

Final Takeaway

The Question to Ask: If it were your elbow or knee with severe osteoarthritis, would you want analgesia? The answer is universally “yes.” Our patients have the same pain pathway, the same feelings, but they cannot advocate for themselves. Recognizing and treating chronic pain is not just medical practice – it is an ethical imperative. Change in behaviour and mobility is the key. Listen to the caregiver, watch the patient, and always consider pain as the source of problem behaviours – especially in older animals.