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Pain causes suffering, stress and anxiety. Every effort should be made to prevent and treat pain in animals to the best of our abilities and minimize suffering. Pain management involves the assessment and treatment of pain.


Our laboratory is a strong advocate for feline welfare and many of our studies provide scientific evidence for pain management. To better treat pain, we first need to be able to recognize it. In mammals, the assessment of pain relies on identifying pain-induced behavioral changes including changes in facial expressions.

Grimace scales are tools used to evaluate pain in animals based on changes in facial expressions and they have been developed in different species. Our laboratory has developed and validated the Feline Grimace Scale, in collaboration with other researchers at the Université de Montréal, to improve feline pain management.

Green Eyed Cat

The Feline Grimace Scale was developed using videos of painful and non-painful cats mostly of client-owned cats presented to the Veterinary Teaching Hospital (CHUV - Centre hospitalier universitaire vétérinaire) of the Faculty of Veterinary Medicine, Université de Montréal. Cats were evaluated and given analgesics (pain killers) if they were found to be painful. The cat owner signed an informed consent for inclusion of the cat in the study. Treatment and care was provided using cat-friendly techniques. None of the manipulations induced pain or harm to the cats.

About: Development
Figure 1a

A camera was attached to the cat’s cage and short videos of the cat before and after administration of analgesics were performed

Images of painful and pain-free cats were compared and five features were identified to be different between these cats. These features, called action units, include:


Ear position

Orbital tightening

Muzzle tension

Whiskers position

Head position

About: Validation


Saying that a scale is ‘validated’ means that rigorous scientific methods were applied to ensure that the Feline Grimace Scale

  • Measures what it is intended to be measured – in this case ‘pain’

  • Is repeatable among different evaluators (similar scores are given by different observers or in other words, different observers "see' the same changes)

  • Is repeatable over time (similar scores are given by the same observer independently of the moment; today or next month, for example)

  • Discriminates between different conditions (painful vs pain-free cats or before and after administration of painkillers)

  • Correlates with a gold-standard (provides similar scores to other very similar valid pain scoring systems used for the same purpose)

  • Detects response to analgesic treatment

The Feline Grimace Scale has shown to be a valid, reliable, fast and simple acute pain assessment in cats.

Licking Cat


Observe the cat undisturbed for 30 seconds and then score. If the cat is grooming, eating or vocalizing, wait until these activities are finished before scoring. If a cat is sleeping, leave it undisturbed and wait until it is awake. ​

Each action unit is individually evaluated and scored as '0' (action unit is absent), '1' (action unit is moderately present or there is uncertainty over its presence) or '2' (action unit is obviously present).

See below examples of each action unit scored as '0', '1' or '2'.

Using the FGS
No pain


0 = Action unit is absent

  • Ears facing forward

  • Eyes opened

  • Muzzle relaxed (round shape)

  • Whiskers loose and curved

  • Head above the shoulder line

Mild to moderate pain


1 = Action unit is moderately present or there is uncertainty over its presence

  • Ears slightly pulled apart

  • Eyes partially opened

  • Muzzle mildly tense

  • Whiskers slightly curved or straight

  • Head aligned with the shoulder line

Moderate to severe pain


2 = Action unit is markedly present

  • Ears flattened and rotated outwards

  • Squinted eyes

  • Muzzle tense (elliptical shape)

  • Whiskers straight and moving forward

  • Head below the shoulder line or tilted down

Interpreting the scores

Higher values indicate more pain. The Feline Grimace Scale helps veterinarians on clinical decision-making and provides guidance to therapy


The FGS has 5 action units that can be scored from 0 to 2. Thus, the maximum possible score is 10. A "cut-off" value (score ≥ 4) suggests that the veterinarian should consider the administration of analgesic drugs taking in consideration the physical status of the patient and other drugs previously administered.

When scores of 4 are obtained and the veterinarian is uncertain whether more analgesics should be administered, the cat should be re-evaluated in 10-15 minutes.

About: Download
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