Signs of Pain in Pets: What Most Owners Miss

Pain is one of the most underrecognized and undertreated conditions in veterinary medicine. The World Small Animal Veterinary Association (WSAVA) Global Pain Council has stated that pain recognition in animals remains “woefully inadequate,” not because veterinarians and pet owners don’t care, but because animals are remarkably effective at concealing their suffering. Understanding why pets hide pain, knowing what to look for across different species, and learning to use the same assessment tools veterinarians rely on can fundamentally change your ability to advocate for your pet’s comfort and well-being.

Why Pets Hide Pain: The Evolutionary Imperative

To understand why your pet doesn’t simply “tell you” when something hurts, you need to understand the evolutionary pressures that shaped their behavior over thousands of years. In the wild, an animal that displays vulnerability — limping, vocalizing, moving slowly — becomes a target for predators. For prey species like birds, rabbits, and reptiles, showing pain is essentially advertising that you are an easy meal. Even predators like dogs and cats have strong instincts to mask weakness, as an injured member of a social group may lose their position in the hierarchy or be abandoned by the pack.

This means that by the time most pets display obvious signs of pain — crying out, refusing to move, or becoming aggressive when touched — the pain is often severe and has been present for much longer than the owner realizes. The key to effective pain recognition is learning to detect the subtle behavioral changes that precede the obvious ones. These subtle shifts are the whispered messages your pet is sending before they start screaming.

Signs of Pain in Dogs

Dogs are generally more expressive than cats about their discomfort, but many of their pain signals are still commonly misinterpreted or overlooked. Research published in veterinary pain journals has identified dozens of behavioral indicators, ranging from obvious to extremely subtle.

Obvious Signs (Often Indicating Moderate to Severe Pain)

• Vocalization: Whimpering, whining, yelping (especially when touched or when moving), growling, or howling. Some dogs, however, become quieter when in pain rather than louder.
• Limping or reluctance to bear weight: Favoring a limb, holding a paw up, or bunny-hopping with the back legs (common in hip dysplasia and cruciate ligament injuries).
• Guarding: Actively protecting a body part by flinching, pulling away, snapping, or biting when that area is approached or touched. A normally gentle dog that growls when you reach for its ear may have an ear infection causing significant pain.
• Trembling or shaking: Pain-related trembling can be distinguished from cold-related shivering by context — if your dog is trembling in a warm room, pain or anxiety should be considered.

Subtle Signs (Often Indicating Mild to Moderate or Chronic Pain)

These are the signs that most owners miss, and they are critically important because they often represent the early stages of a painful condition when treatment is most effective:

• Changes in panting patterns: Dogs pant to cool down, but panting at rest, at night, or in cool environments can indicate pain. This is one of the most commonly overlooked pain indicators in dogs. Orthopedic pain, abdominal discomfort, and systemic illness can all cause inappropriate panting.
• Pacing and restlessness: A dog that cannot settle, repeatedly gets up and lies down in different positions, or paces the house at night may be experiencing pain that prevents them from finding a comfortable position. This is especially common with abdominal pain, spinal pain, and bloat.
• Changes in posture: A hunched back (indicating abdominal or spinal pain), a “prayer position” with the front end down and back end up (classic for pancreatitis and abdominal pain), a stiff gait, reluctance to sit or lie down, or difficulty rising from a resting position.
• Appetite changes: Pain frequently causes decreased appetite or a complete refusal to eat. Dogs with dental pain may approach the food bowl eagerly but then eat slowly, drop food, or walk away. They may prefer soft food over kibble or chew only on one side.
• Decreased activity and social withdrawal: A dog that stops greeting you at the door, no longer wants to play, avoids stairs it previously climbed easily, or stops jumping onto furniture may be in pain. Owners frequently attribute these changes to “getting old,” but aging alone does not cause pain — specific conditions that happen to be more common in older dogs (arthritis, dental disease, cancer) cause the pain.
• Sleep disturbances: Difficulty getting comfortable, frequent repositioning during sleep, or restlessness at night. Dogs with orthopedic pain often struggle to find a comfortable sleeping position.
• Excessive licking or chewing: Dogs may lick or chew at a painful area obsessively, leading to “lick granulomas” — areas of hair loss and thickened, irritated skin. However, the licking is not always directly over the site of pain. Dogs with referred pain may lick their paws or legs even when the primary pain source is in the spine or abdomen.
• Changes in facial expression: Research from the University of Lincoln has developed a canine “grimace scale” documenting that dogs in pain display specific facial changes including narrowed or partially closed eyes, flattened ears, tense muscles around the muzzle, and a furrowed brow. These expressions are subtle but measurable.

Signs of Pain in Cats

Cats are widely considered the most difficult common companion animal to assess for pain. Their evolutionary history as both predator and prey has given them an extraordinary ability to mask discomfort. A landmark 2016 study published in PLOS ONE developed the Feline Grimace Scale, and subsequent research has continued to refine our understanding of feline pain expression.

Behavioral Changes Indicating Pain in Cats

• Hiding: One of the most common and most easily dismissed pain signs in cats. A cat that suddenly starts spending all its time under the bed, in the back of a closet, or in other secluded areas may be in pain. While cats do enjoy quiet spaces, a sudden increase in hiding behavior — especially in a previously social cat — warrants investigation.
• Changes in grooming habits: This is a nuanced sign because pain can cause either decreased grooming or increased grooming. A cat in generalized pain or feeling systemically unwell will often stop grooming, leading to a dull, unkempt coat with mats or dandruff. Conversely, a cat with localized pain (such as a urinary tract problem, skin condition, or joint pain) may over-groom the affected area, sometimes to the point of creating bald patches or skin sores. Over-grooming of the belly and inner thighs, for instance, is commonly associated with lower urinary tract pain, abdominal discomfort, or stress.
• Litter box changes: A cat that begins urinating or defecating outside the litter box, straining in the box, visiting the box more frequently, or vocalizing while using the box may be experiencing pain. Urinary pain (from cystitis, crystals, or blockage) and arthritis pain (making it difficult to climb into a high-sided box) are common culprits. Many cats surrendered to shelters for “behavioral” litter box issues actually had undiagnosed pain conditions.
• Aggression or irritability: A previously friendly cat that begins hissing, swatting, or biting when picked up, petted, or approached may be in pain. This is not “bad behavior” — it is a cat communicating, in the only way it can, that being touched hurts. Pay particular attention to aggression that is localized — a cat that is fine with being petted on the head but attacks when you touch its back may have spinal pain.
• Purring: This is perhaps the most counterintuitive pain sign. While cats purr when content, they also purr when injured, frightened, or in pain. Research suggests that the vibration frequency of purring (25–150 Hz) may have self-healing properties, stimulating bone density and tissue repair. A cat that is purring while showing other signs of distress (hiding, not eating, tense posture) is likely purring as a self-soothing mechanism, not because it is happy.
• Decreased jumping and climbing: Cats with arthritis or other musculoskeletal pain will gradually stop jumping onto counters, windowsills, or cat trees they previously frequented. They may use intermediate surfaces to reach high places (jumping to a chair first, then to the counter) rather than jumping directly. Many owners don’t notice this gradual reduction in vertical activity.
• Changes in facial expression: The Feline Grimace Scale (FGS), validated in clinical settings, identifies five facial features that change with pain: ear position (ears rotated outward and flattened), orbital tightening (squinting or partially closed eyes), muzzle tension (a tense, elongated appearance), whisker position (whiskers pushed forward and away from the face), and head position (head held below the shoulder line). Each feature is scored 0–2, with a total score of 4 or above (out of 10) indicating clinically significant pain.

Signs of Pain in Birds

Birds are prey animals par excellence, and their pain-masking abilities are arguably the most extreme among common companion animals. A bird that shows obvious signs of illness or pain in the wild is immediately vulnerable to predation. This means that a pet bird showing visible symptoms is often already seriously ill or in significant pain.

• Fluffed feathers: A bird sitting with its feathers puffed out (not during normal preening or sleeping) is attempting to conserve body heat, which often indicates illness, pain, or both. Persistently fluffed feathers during the day are one of the most reliable indicators that something is wrong.
• Sitting on the cage floor: Healthy birds perch. A bird sitting on the bottom of its cage, especially during the day, is demonstrating significant weakness, pain, or illness. This is almost always an emergency sign that warrants immediate veterinary attention.
• Decreased or absent vocalization: A bird that stops singing, talking, or vocalizing — especially one that is normally vocal — may be in pain or feeling too unwell to vocalize. Conversely, some birds may vocalize more with certain types of acute pain, producing distress calls or unusual sounds.
• Changes in eating and drinking: Decreased food consumption, dropping food, or difficulty manipulating food can indicate beak pain, crop problems, or systemic illness causing oral pain or nausea.
• Favoring a foot or wing: Holding a wing drooped, refusing to use one foot for perching, or shifting weight repeatedly from foot to foot can indicate injury, arthritis, or bumblefoot (pododermatitis).
• Self-mutilation: Feather plucking and self-mutilation can have many causes, but pain should always be considered, particularly if the behavior is focused on a specific body area.
• Changes in posture: A bird that sits with eyes partially closed during the day, bobs its tail with each breath (indicating respiratory effort), or holds its body in an unusual position may be in pain.

Signs of Pain in Reptiles

Reptile pain recognition is one of the most challenging areas in veterinary medicine. For decades, there was debate about whether reptiles even experience pain, but modern neuroscience has conclusively demonstrated that reptiles possess nociceptors (pain-sensing nerve fibers) and the neural pathways necessary for pain perception. The challenge is that reptile behavioral responses to pain are far more subtle and alien to mammalian observers than those of dogs and cats.

• Color changes: Many reptile species undergo color changes in response to stress and pain. Darkening of the skin (particularly in bearded dragons, chameleons, and anoles) can indicate discomfort. A bearded dragon that displays a persistently dark or black “stress beard” may be in pain.
• Cessation of basking: Healthy reptiles thermoregulate by basking under heat sources. A reptile that stops basking, spending its time in the cooler end of the enclosure, may be experiencing pain or illness. Paradoxically, some reptiles with infections may seek higher-than-normal temperatures (behavioral fever) to support their immune response.
• Anorexia: Refusal to eat is one of the more reliable pain indicators in reptiles, but it must be interpreted in context — many reptiles fast during brumation (seasonal dormancy), shedding, or breeding season. Anorexia outside these expected periods, especially combined with other behavioral changes, is concerning.
• Decreased movement or abnormal posture: A snake that holds its body rigidly or does not coil normally, a lizard that drags a limb or tilts its body, or a turtle/tortoise with an asymmetric gait may be experiencing musculoskeletal pain. Reptiles with metabolic bone disease (MBD) often show tremors, rubber-like jaw flexibility, and reluctance to move due to pathological fractures.
• Defensive behavior changes: A normally docile reptile that becomes aggressive when handled, especially when a specific area is touched, may be in pain. Conversely, a normally defensive reptile that becomes unusually passive or limp may be too painful or debilitated to mount a normal defensive response.
• Eye changes: Closed or sunken eyes in reptiles often indicate systemic illness and pain. In snakes, retained eye caps (spectacles) can cause significant irritation and discomfort.

Pain Assessment Scales Used by Veterinarians

Veterinary medicine has developed validated pain assessment tools to bring objectivity and consistency to pain recognition. Understanding these scales can help you communicate more effectively with your veterinarian about your pet’s pain level.

Glasgow Composite Pain Scale (GCPS) – Dogs

The Glasgow Composite Pain Scale is one of the most widely used and well-validated pain assessment tools in veterinary medicine. Developed at the University of Glasgow, it evaluates pain across multiple behavioral categories: vocalization, attention to the wound/painful area, mobility, response to touch, demeanor, and posture/activity. Each category is scored on a descriptive scale, and the composite score provides an overall pain severity rating. A score above a defined intervention threshold indicates that pain treatment should be administered or adjusted. The short form (CMPS-SF) is commonly used in clinical settings and includes 6 behavioral categories and 1 category for overall impression.

Colorado State University Pain Scales

Colorado State University developed widely used visual pain scales for both dogs and cats. These scales combine behavioral descriptors with illustrations showing typical body language at each pain level, ranging from 0 (pain-free) to 4 (severe pain). The canine scale emphasizes body tension, facial expression, and response to palpation. The feline scale, recognizing the unique challenges of cat pain assessment, places particular emphasis on facial expression, body position, and activity level. These scales are designed to be user-friendly and are used in veterinary clinics, teaching hospitals, and research settings worldwide. Many veterinary practices have these charts posted in treatment areas for quick reference.

Feline Grimace Scale (FGS)

Developed by researchers at the Université de Montréal and published in 2019, the FGS specifically addresses the challenge of pain assessment in cats. It evaluates five facial action units: ear position, orbital tightening, muzzle tension, whisker change, and head position. The FGS has been validated as reliable and accurate, with a total score ≥4 out of 10 indicating the need for analgesic intervention. What makes the FGS particularly valuable is that it can be used from a distance without handling the cat, which is important because handling a painful cat may alter its behavior and mask or exacerbate signs.

Chronic Pain vs. Acute Pain

Understanding the distinction between acute and chronic pain is essential for effective pain management in pets.

Acute Pain

Acute pain has a clear onset and is directly associated with tissue damage — surgery, injury, infection, or an acute disease process. It serves a protective biological function, alerting the animal (and the observant owner) that something is wrong. Acute pain tends to produce more obvious behavioral changes: vocalization, guarding, limping, restlessness, and changes in vital signs (elevated heart rate, respiratory rate, and blood pressure). Treatment focuses on addressing the underlying cause while providing analgesic support. With appropriate treatment, acute pain resolves as the tissues heal.

Chronic Pain

Chronic pain persists beyond the expected period of healing and often no longer serves a protective function. Osteoarthritis is the most common cause of chronic pain in dogs and cats, affecting an estimated 80% of dogs over age 8 and 90% of cats over age 12 (though the prevalence in cats was dramatically underrecognized for decades). Chronic pain produces gradual behavioral adaptations that are easily missed because they develop slowly over weeks, months, or years. Owners accommodate their pet’s declining function — adding steps to help them onto the bed, switching to lower-sided litter boxes, shortening walk distances — without recognizing that these accommodations are compensating for pain.

The WSAVA Global Pain Council emphasizes that chronic pain, particularly osteoarthritis, is one of the most significant welfare issues in companion animal medicine today. The tragedy is not that these animals cannot be helped — modern pain management offers numerous effective options — but that the pain is so often unrecognized until it is severe.

When to See the Veterinarian

If you observe any of the pain signs described in this guide, a veterinary evaluation is warranted. The urgency depends on the severity and nature of the signs:

• Emergency (go now): Severe, sudden-onset pain (vocalization, collapse, inability to move), signs of pain combined with difficulty breathing, abdominal distension, or pale gums, suspected trauma or fracture, bird sitting on cage floor or severely fluffed
• Urgent (same day or next day): Moderate pain signs (limping, guarding, significant behavior changes), acute onset of any pain sign in a previously normal pet, signs of pain combined with vomiting, diarrhea, or fever
• Schedule an appointment (within 1–2 weeks): Subtle, gradual behavior changes suggesting chronic pain (decreased activity, reluctance to jump, stiffness, changes in grooming patterns), especially in senior pets

Pain Management Options

Modern veterinary pain management is multimodal, meaning it combines multiple approaches for the most effective relief:

• NSAIDs (Non-Steroidal Anti-Inflammatory Drugs): Carprofen (Rimadyl), meloxicam (Metacam), and others are the foundation of pain management for many conditions in dogs. Meloxicam at appropriate doses and robenacoxib (Onsior) are options for cats. These medications should only be used under veterinary supervision with appropriate monitoring (baseline and periodic blood work).
• Opioids: Buprenorphine, tramadol, and other opioids are used for moderate to severe pain, particularly post-surgical pain. Buprenorphine is particularly useful in cats due to effective transmucosal (oral mucosa) absorption.
• Gabapentin: Originally an anticonvulsant, gabapentin has become widely used for neuropathic pain and as an adjunct pain medication in both dogs and cats. It is also used as an anxiolytic to reduce stress during veterinary visits.
• Monoclonal Antibody Therapy: Bedinvetmab (Librela for dogs) and frunevetmab (Solensia for cats) are newer biologic therapies that target nerve growth factor (NGF), a key mediator of osteoarthritis pain. These monthly injections have shown significant efficacy with minimal side effects and represent a major advancement in chronic pain management.
• Physical rehabilitation: Veterinary physical therapy, hydrotherapy (underwater treadmill, swimming), laser therapy, acupuncture, and therapeutic exercises can significantly improve comfort and function, particularly for orthopedic and neurological pain.
• Weight management: For overweight pets with musculoskeletal pain, weight loss alone can produce dramatic improvement. Studies have shown that achieving a healthy body weight can reduce the need for pain medication in dogs with arthritis.
• Environmental modifications: Ramps instead of stairs, orthopedic beds, raised food and water bowls, low-sided litter boxes, non-slip flooring, and heated beds can all reduce pain and improve quality of life for pets with chronic pain conditions.

The WSAVA Global Pain Council’s guidelines emphasize that pain management is not optional — it is a fundamental component of ethical veterinary care and responsible pet ownership. Every animal deserves to have its pain recognized, assessed, and treated. By learning to read the subtle signals your pet sends, you become their most important advocate in the pursuit of comfort and quality of life.

Disclaimer: This article is for educational purposes only and does not constitute veterinary advice. Always consult with a qualified veterinarian for specific health concerns about your pet. See our Medical Disclaimer for complete details.

Last updated: March 2026 · Editorial Standards