Pain is widely recognized in veterinary medicine as the fourth vital sign, pushing recognition and quantification of pain to the forefront of many daily examinations in a typical clinical practice. This is true for all sentient animals, including farmed animal species, exotics, fish, companion animals, wildlife, and laboratory animals.1
It has been estimated approximately 45 per cent of all cats show clinical signs of chronic pain, which is frequently related to degenerative joint disease (DJD).2 The onset of DJD is slowly progressive in most instances, leaving chronic pain in cats underdiagnosed and undertreated. This results in negative consequences for the animal’s quality of life (QoL) and can also harm the human-animal bond.2,3 Likewise, in dogs, clinical signs of chronic pain are typically subtle and vary between individuals, leading to under-recognition, undertreatment, and negative impact on the QoL for these patients.4
In human medicine, pain assessment is generally fairly straightforward, as most of these patients can communicate to their doctors where they hurt, what the pain feels like, and its severity. The same is not true for pain assessment in animals. For veterinary team members, identifying pain in our animal patients remains a challenge.
Pain is an unpleasant conscious, multi-dimensional experience that is influenced by previous pain experience, sensory input, and psychological factors. As such, veterinarians need to be able to assess and interpret the patient’s history, mobility, response to exam, and behaviours in order to determine the impact of pain on a specific animal. The best way to achieve this is to look at assessment tools that are reliable, sensitive, reproducible, and validated.
A significant concern for pet owners and veterinarians is the effect of pain on QoL and, more specifically, the effect of disease on QoL (this is commonly referred to as the Health-Related Quality of Life, or HRQoL).4 Several tools have been developed to measure HRQoL. While these measures are not widely published or available at this time,3 many of these pain assessment tools incorporate elements of QoL.
Indeed, multiple tools exist to help veterinary teams assess and monitor pain in our patients.1 These can be divided into acute and chronic assessment tools and are specific to the species being examined. It is important veterinary teams use the same assessment tools over time to provide a reliable measure of treatment success for an individual patient, as well as create a sense of familiarity with the tools you are using. With repeated use, these tools become easier and faster to use, which, in turns, helps increase compliance.
The role of registered veterinary technicians (RVTs) in the evaluation of pain is incredibly important. These professionals are most often directly involved in patient care and can use these tools to evaluate patients in hospital, reporting to the treating veterinarian to assess the need for intervention. RVTs are also invaluable at explaining the use of chronic pain tools to pet owners for at home use.
This article offers an overview of the assessment of pain using validated tools in canine and feline patients.
Validated tools used to assess acute pain are typically divided into two components:
- Observational, which may utilize posture, vocalization, facial expression, response to people, and attention to a wound, along with the general attitude of the patient.
- Interactive, such as response to palpation of a wound. (Mechanical threshold testing has been used to evaluate hyperalgesia in animals, suggesting wound manipulation is a reasonable direct test for wound pain.)
In cats, behavioural and physiologic features are affected by pain; however, other features, including blood pressure, heart and respiratory rates, and pupil size, are influenced by fear and stress and, as such, are not reliable indicators of pain in a typical clinical setting.3 The observational component of these tools will be specific to the species being assessed and, ideally, consider the patient’s behaviour before surgery or other painful interventions. Animals that are fearful or aggressive before surgery will behave differently than passive animals, whether pain is present or not; however, facial expression, changes in posture, and demeanour can still be observed and recorded. Systems that have been developed to measure these parameters (and have been tested and validated) provide the most reliable pain assessment tools for acute pain.
Most tools used to assess chronic pain rely on changes in the normal behaviours, movement, and activity of the patient. Clinicians can ask clients to film their pets’ normal behaviour at home to highlight abnormal activities that may not be observed in the clinic setting.
While the development of accelerometers for home use may one day help detect changes in activity at home, there is currently no strong data to support their use for pain evaluation. Additionally, objective measures, such as force plate and vertical force analysis, are not practical in everyday practice and are not completely reliable as an indicator of pain.
Feline acute pain assessment
The most recently validated tool for acute pain assessment in cats is the Feline Grimace Scale (FGS).5 This tool was developed for use by veterinary teams, as well as members of the public. The scale is easy to use, does not require handling of the patient, and, importantly, is reliable.
The Feline Grimace Scale utilizes distant observation of a cat’s facial expression and head position. Ear position, orbital tightening, muzzle tension, whisker position, and head position are each scored on a scale of 0 (normal) to 2 (marked change from normal), for a maximum total score of 10. Intervention with analgesics is recommended at scores of 4 or greater. The FGS is available for free in the app store and can be downloaded in English, French, or Spanish.
The short version of the UNESP-Botucatu Cat Pain Scale (UCAPS)6 has been validated for any type of acute pain in cats. This scale assesses four parameters: activity, body posture, general attitude, and response to palpation of a painful site. Each parameter is scored from 0 (normal) to 3 (marked change form normal). The maximum score is 12, with analgesic intervention recommended for scores of 4 or higher. If a cat is fractious and cannot be safely handled, the scale allows the palpation scoring to be removed for a maximum score of 9, with intervention recommended for scores of 3 or higher. This pain scale has now been validated in eight languages.
The Glasgow Composite Measure Pain Scale-Feline (CMPS-Feline)7 has been validated for all types of acute pain in cats. This tool utilizes seven measures to assess pain: vocalization, posture, attention to the wound, response to people, response to palpation of the wound, overall demeanour, and facial expressions. These parameters have variable ranges of scores with a maximum score of 20. Rescue analgesia is recommended for scores of 5 or greater.
With a little practice and consistent use of any of these three scales, all veterinary team members can rapidly and reliably evaluate acute pain in feline patients.
Feline chronic pain assessment
As mentioned above, DJD pain affects a significant percentage of our feline patients. The Feline Musculoskeletal Pain Screening Checklist (Feline MiPSC) was developed as a quick and reliable initial screening test, and to increase awareness of osteoarthritis (OA) in cats. It is available in the article where it was originally published,8 but it has not been published as a standalone scale. The checklist contains six “yes/no” questions about specific activities. If an owner answers “no” (i.e. the activity is not normal) to any of the six questions, this should prompt further evaluation of OA-related pain using a specific chronic pain assessment tool for cats, such as:
- The Feline Musculoskeletal Pain Index (FMPI), which is a validated scale for use on chronic pain arising from degenerative joint disorders.9 This scale is designed to be used by the client by observing 17 different movements at home, as well as assessing two QoL statements.
- A Client Specific Outcomes Measure (CSOM) tool. This is similar in intent to the FMPI, but utilizes only three outcome measures for mobility and activity, which are chosen by the client for their individual cat.10 Though not currently validated, this tool is simple to use, tailored to the individual patients, and allows the client to assess the pet in their home environment.
Canine acute pain assessment
The Glasgow Composite Measure Pain Scale-Short Form (CMPS-SF)11 has been developed for the assessment of acute pain in dogs. It utilizes six categories to assess: vocalization, attention to the painful area, ease of rising and walking, response to palpation, overall attitude, and posture. The maximum score is 24, with analgesic intervention recommended for scores of 6 or higher. If the patient’s mobility cannot be assessed, the maximal score is 20 with intervention for scores 5 or higher.
The Melbourne Pain Scale (UMPS) was developed in dogs undergoing ovariohysterectomy. It includes multiple descriptors in six categories of data or behaviours associated with response to pain. Categories include physiological data, response to palpation, activity, mental status, posture, and vocalization. A maximum score is achieved with 27 points.12
The Colorado State University Acute Pain scale (available at csu-cvmbs.colostate.edu) has been developed from three other scales and utilizes drawings of dogs that fit into five observational categories, as well as a physical assessment of the patient. While this tool is simple and quick to use and widely cited, it has not been validated. As such, other validated tools should preferentially be used.
Canine chronic pain assessment
The Canine Brief Pain Inventory (Canine BPI) is an owner-generated pain tool that looks at six normal activities: rising to stand, walking, running, climbing, enjoyment of life, and general activity.13 It assesses each of these based on severity of impact of pain on the activity. There is also a global QoL question. This tool can be used by an animal’s owners before any treatments to set a baseline, then used during treatment to measure any response to treatment.
The Helsinki Chronic Pain Index14 and the Liverpool Osteoarthritis in Dogs (LOAD)15 indices are similar tools, utilizing owner-derived information to assess a dog’s mobility, normal movements, and impact on the pain on their life. These two tools have been validated, but are not as frequently used in clinical practice as the CBPI.
Finally, the Canine Osteoarthritis Staging Tool (COAST) uses a combination of a clinical metrology tool that is owner-assessment based, in addition to a veterinary examination of the dog’s overall impairment and a specific examination of any affected joints.16 The values are totalled to create a disease severity score, which can be used to direct appropriate levels of intervention. This tool is more complex to administer and is used more often in a research setting, but not in daily practice.
What does the future of pain assessment look like?
The development of wearable and remotely uploaded data may be the way of the future for assessing pain in veterinary medicine. While there are currently no validated or widely researched tools utilizing these types of technologies, PainTrace17 is one electronic device available, which utilizes an electronic monitor attached to an animal during a full orthopedic and pain assessment. The tool digitally records the areas where pain is being registered by the animal during the exam, along with the amplitude of that pain. The device can be used for dogs and cats to assess both acute and chronic pain, and can used repeatedly to monitor response to treatment. Moving forward, it will be interesting to see if this type of device can be validated and reliably used in clinical practice.
Jim Berry, DVM, CVPP, owner of Douglas Animal Hospital in Fredericton, has worked in clinical practice for 32 years in three different areas of Canada. He has spent the past 15 years focused on companion animal lameness and pain management, employing an integrated approach to patient care. Dr. Berry is certified in veterinary acupuncture (IVAS), canine rehabilitation (CRI), and animal chiropractic (Options for Animals). He is also actively involved in veterinary association work across Canada and beyond, serving on executive boards and various committees of the New Brunswick Veterinary Medical Association, the Canadian Veterinary Medical Association, the World Small Animal Veterinary Association, and the International Veterinary Academy of Pain Management.
1 Monteiro BP, Lascelles BDX, Murrell J, Robertson S, Steagall PVM, Wright B. 2022 WSAVA guidelines for the recognition, assessment, and treatment of pain. Journal of Small Animal Practice 2022 Oct. https://doi.org/10.1111/jsap.13566
2 Masataka E, Lascelles BDX, Robertson JB, Gruen ME. Refinement of the Feline Musculoskeletal Pain Index (FMPI) and development of the short-form FMPI. Journal of Feline Medicine and Surgery 2022;24(2): 142–151. doi: 10.1177/1098612X211011984. https://pubmed.ncbi.nlm.nih.gov/34002643
3 Monteiro BP, Steagall P. Chronic pain in cats: Recent advances in clinical assessment. Journal of Feline Medicine and Surgery 2019 July;21(7): 601–614. doi: 10.1177/1098612X19856179. https://pubmed.ncbi.nlm.nih.gov/31234749
4 Belshaw Z, Yeates J. Assessment of quality of life and chronic pain in dogs. The Veterinary Journal 2018 Sep;239: 59-64. doi: 10.1016/j.tvjl.2018.07.010. https://pubmed.ncbi.nlm.nih.gov/30197111
5 See: https://felinegrimacescale.com
6 See: https://animalpain.org/en/home-en
7 See: https://newmetrica.com/acute-pain-measurement
8 Masataka E, Lascelles BDX, Gruen ME. Development of a checklist for the detection of degenerative joint disease-associated pain in cats. Journal of Feline Medicine and Surgery 2020;22(12): 1137-1147. doi:10.1177/1098612X20907424. https://journals.sagepub.com/doi/full/10.1177/1098612X20907424
9 See: https://painfreecats.org
10 Download here: https://cvm.ncsu.edu/wp-content/uploads/2019/11/CSOMf-instructions-2019-11.pdf
11 See: https://newmetrica.com/acute-pain-measurement
12 The UMPS is available via the originally published: Firth AM, Haldane SL. Development of a scale to evaluate postoperative pain in dogs. J Am Vet Med Assoc 1999 Mar;214(5): 651-9. https://pubmed.ncbi.nlm.nih.gov/10088012
13 See: https://www.vet.upenn.edu/research/clinical-trials-vcic/our-services/pennchart/cbpi-tool
14 See: https://www.fourleg.com/media/Helsinki%20Chronic%20Pain%20Index.pdf
15 See: https://bit.ly/3Dz39Ap (via Penn Vet)
16 See: https://www.galliprantvet.com/us/en/coast-tools
17 See: https://paintrace.com