Since my very first steps in the animal osteopathy world, I was confronted with pain in animals and brought to assess it from all angles. I realised that often, pain is present for months, even years, before we notice it. Yet animals show us, sometimes very clearly, when they are in pain.
Even with the best of intention, our interpretation of the horse body language is not always reliable. A grimace can be perceived as a bad temper, a tense face interpreted as adrenaline kicking in, a tired eye can be deduced as relaxation or laziness.
For owners as well as professionals, it is easy to assume wrong.
It is still not customary to make sure a horse is comfortable by analysing their facial expressions... no lameness, no swelling, no trace of injury whatsoever, the horse must be just fine. However, without necessarily being able to pinpoint the why and how, certain signs can alert us, and give us the feeling that something is not quite right.
For therapists, the first approach is observation where each physical and behavioral detail will be analysed.
I once heard of Equine Pain Face scale, researched what these parameters are based on and what it all really means. My goal was to know exactly what to recognise during a first approach and how not to let slip a potential discomfort or even an illness hidden behind a horse in apparent good physical condition.
In all fields and environments, how many horses are misunderstood and experience pain in silence?
When the expression of pain is understood and recognised, it does not go away.
What is pain concretely?
Definition: “Localised or generalised unpleasant bodily sensation or complex of sensations that causes mild to severe physical discomfort and emotional distress and typically results from bodily disorder (such as injury or disease).”
There are two main types of pain:
- Nociceptive pain: the most common, arises from various kinds of trouble in tissues, reported to the brain by the nervous system. It is everything from a horse kick with open wound to repetitive tendonitis, tumours, and inflammatory arthritis. Nociceptive pain typically changes with movement, posture, and compensation.
- Neuropathic pain: complex to diagnose as it arises from damage to the nervous system itself. The possible sources are wide, anything that damages neurons cause horses to become extra sensitive to a stimulus. What normally wouldn't hurt can create excruciating pain, causing the animal to react sometimes violently and for no apparent reason. It is also more likely to lead to chronic pain.
Emotions and facial expressions are intimately and firmly connected. Persistent pain will lead to emotional imbalances in the host which will generally lead to a physical marker. Facial expressions are therefore influenced by pain and reveal specific indicators which are difficult to camouflage. Furthermore, facial expressions are even considered to be the most consistent pain expression in children. Charles Darwin predicted that animals could exhibit similar facial expressions in response to emotional states as humans do, but it is only recently that facial expressions started to be used to evaluate pain.
The Equine Pain Scale is based on several experiments carried out on horses using methods that would make most people wince. Each time, horses were subjected to different sources of pain (either induced for the experiment or induced for a necessary intervention, such as castration) and were observed by behavioral scientists. Skipping the specific details of the experiments, we know that the results were conclusive: all the horses showed the same signs, more or less extreme according to the intensity of the stimuli applied.
Horse during pain induction
Equine pain face experiment
Here are the 5 signs that deserve your attention:
- Ears: Lowered ears, turned simultaneously outward, often move, or are positioned asymmetrically
- Eyes: The muscles around the eye are tight especially in the upper arch which gives the eyelid a distinctive angular appearance. A stare glance, withdrawn look, inanimate gaze are also signs to consider.
- Nostrils: The nostrils are dilated in a side-to-side direction, drawing more angular shapes, and forming sharper edges, especially noticeable in the medial part of the nostrils.
- Face Muscles: the soft tissues to the side of the horse’s head have an irregular appearance with sometimes formation of “tension lines”
- Muzzle: Increased tonus of the lips that are pressed together and tension of the chin which appears flattened and hard to the touch. Overall, more edged shape of the muzzle.
(a) Facial expression of a pain free, relaxed and attentive horse
(b) Facial expression of a horse in pain, all features of the pain face including asymmetrical ears
(c) Facial expression of a horse in pain, all features of the pain face including low ears
(Ill. Andrea Klintbjer)
Evaluating the facial expression of the horse should be done when there are no distractions nearby and the environment is conducive to an observation. All observer must consider the body language of the animal, and not to interact with them during observation. It is also possible to assess a mounted horse but the external elements must be taken into consideration for a correct analysis (rider's level, tack fitting, ground's quality, athletic requirements) as these may vary facial expressions. In both cases, more than one feature mentioned above is present when a horse is in pain.
It is essential to know how to interpret the facial and behavioral signs that our horses show us in order to stay up to date on their physical and mental state. Thus, a problem that could go unnoticed and worsen over months or years can be detected quickly, treated, and eliminated.
If you’d like to know more on this subject, here are some sources I used for this article and do not hesitate to reach for your veterinarian or your equine therapist if you notice multiple signs from the Equine Pain Scale on your horse.
The Equine Pain Scale Dr Kelly Gowland Equine Health, News, 2021
Development of an ethogram to describe facial expressions in ridden horses (FEReq) Jessica Mullard, Jeannine M. Berger, Andrea D. Ellis, Sue Dyson, Journal of Veterinary Behavior, 2017
An equine pain face Karina B Gleerup, Bjorn Forkman, Casper Lindegaard & Pia H Andersen, Vet Anaesth Analg, 2015
Development of the Horse Grimace Scale (HGS) as a pain assessment tool in horses undergoing routine castration
E Dalla Costa, M Minero, D Lebelt, D Stucke, E Canali, MC Leach - PLoS one, 2014
Judgments of genuine, suppressed, and faked facial expressions of pain Poole, G. D., & Craig, K. D. Journal of Personality and Social Psychology, 1992
Pain expression in patients with shoulder pathology: validity, properties and relationship to sickness impact KM Prkachin, SR Mercer - Pain, 1989