The Horse Pain Face: How to Recognize It and What to Do

Horses in pain change their faces in consistent, measurable ways, and research over the past decade has mapped those changes precisely enough that trained owners and caretakers can learn to spot them. The shifts involve the ears, the eyes, the nostrils, the muzzle, and the jaw muscles, and they can appear together or in partial combinations depending on the type and intensity of pain. A formal scoring system called the Horse Grimace Scale now gives people a structured way to read what a horse’s face is telling them, but even without memorizing the scoring sheet, knowing what to look for can be the difference between catching a problem early and missing it entirely.

What the Pain Face Actually Looks Like

The most detailed experimental work on the equine pain face comes from controlled studies where researchers induced brief, reversible pain in horses and filmed the resulting facial changes. Every horse in these studies showed altered facial expressions during pain, and the changes fell into distinct, repeatable patterns across the ears, eyes, nostrils, and muzzle.¹ These are not subtle, ambiguous signals. Once you know what a relaxed horse’s face looks like, the pain version is strikingly different.

The ears are often the first thing people notice. During pain, horses tend to drop their ears slightly down and to the sides, and the bases of the ears spread apart. They spend more time with ears held low or moving asymmetrically, rather than pricked forward in the alert, attentive position. A horse that normally swivels its ears freely to track sounds may hold them fixed and rotated outward instead.¹

The eyes change in a way that, once you’ve seen it, is hard to miss. The muscles around the eye tighten, especially above the upper eyelid, creating an angled or triangular appearance. In some horses, this tightening pulls the eyelid shape enough to expose the white of the eye at the inner corner. The gaze itself shifts from relaxed and open to withdrawn and fixed, sometimes described as an intense stare that seems directed inward rather than at anything in the environment.¹

The nostrils change shape. Instead of the normal elongated oval, they widen and flatten into a more squared-off appearance. The inner wing of the nostril flares medially, sometimes constantly and sometimes just on each breath in, while the nostril also widens to the side. The overall effect is a horse that looks like it is flaring its nostrils even when breathing is otherwise normal.

The mouth and chin tighten. The lips press together, the chin muscles tense, and the muzzle takes on a more angular, edged appearance. Along the side of the head, the muscles that pull the lip corners back become more visible. Some horses clench their jaw, making the masseter muscle stand out. The combined effect of all these changes is a face that looks tense, angular, and drawn compared to the soft, rounded features of a comfortable horse.¹

The Horse Grimace Scale

Researchers formalized these observations into a scoring tool called the Horse Grimace Scale, or HGS. It was originally developed using horses undergoing routine castration, comparing their facial expressions before and after surgery. The scale breaks the pain face into six specific facial action units, each scored on a scale from not present to obviously present.²

Those six action units are:

• Stiffly backward ears: ears pinned back or held rigidly rather than moving freely.
• Orbital tightening: the muscles around the eye squeeze, partially closing or distorting the eye shape.
• Tension above the eye: visible contraction of the muscles on the brow, sometimes creating a furrowed or angled look above the eyelid.
• Strained chewing muscles: the jaw muscles become visibly prominent and tense.
• Strained mouth and pronounced chin: the lips press together and the chin tightens, giving the lower face a rigid, angular look.
• Strained nostrils and profile flattening: the nostrils take on that squared shape, and the overall profile of the face appears flatter or more tense.

Not all six need to be present at once for a horse to be in pain. The expression is dynamic and shifts as the horse reacts to things in its environment. A horse in moderate discomfort might show three or four of these changes, while a horse in severe acute pain is more likely to display all of them simultaneously. The key is recognizing that any combination of these facial shifts, especially when they persist or recur, warrants closer attention.¹

How Reliable Is Facial Pain Scoring?

A reasonable question is whether different people looking at the same horse would agree on what they are seeing. The answer, based on systematic reviews of the evidence, is that facial-expression-based pain assessment in horses has excellent agreement between observers. A meta-analysis of pain assessment studies found inter-observer reliability scores above 0.90 for colic, post-castration pain, and head-related pain. That level of consistency means trained observers are reading the same signals with high agreement, which is better than many other pain assessment methods in veterinary medicine.³

The practical takeaway is that facial expression scoring is not just a lab curiosity. It translates to real clinical settings and can be performed by people who are not pain researchers, provided they have some training in what to look for. That makes it potentially useful for barn managers, experienced owners, and veterinary technicians, not just board-certified veterinarians.

Spotting Pain Under Saddle

Pain assessment gets more complicated when a horse is being ridden. The movement, the contact with the bit, and the rider’s aids all influence ear and mouth position in ways that can overlap with pain signals. Research using a facial expression ethogram designed specifically for ridden horses found that lame horses had significantly higher pain scores than sound horses, and that certain indicators were particularly telling: being severely above the bit, twisting the head, an asymmetrical bit position, ears pinned back or held in mismatched positions, exposed whites of the eye, partially closed eyes, and an intense stare.⁴

When lameness was treated and resolved, the facial pain scores dropped. Total pain score, head position score, and ear scores all improved after the source of lameness was addressed.⁴ This is one of the more useful findings for everyday riders, because it means that facial expression during work is not just noise. If you are riding a horse that consistently pins its ears, exposes the whites of its eyes, or holds its head at unusual angles, pain should be on the list of explanations alongside behavioral issues or training problems.

Riders sometimes attribute these signals to a “bad attitude” or resistance. The research suggests that a significant number of horses showing these behaviors are dealing with musculoskeletal pain that a lameness exam could identify. Taking the horse’s face seriously under saddle can short-circuit months of frustration and misguided training interventions.

When the Face Does Not Tell the Whole Story

Facial pain assessment is powerful but has real limitations. One important finding from experimental work is that pain expressions fade as the horse becomes drowsy. In studies where pain was induced with capsaicin, horses began showing signs of drowsiness after about fifteen minutes on average, and as drowsiness set in, the pain face became less pronounced.¹ This means a horse that looks relaxed and sleepy may still be in pain, especially if it has been dealing with discomfort for a while. Drowsiness can mask what the face would otherwise show.

Breed and individual variation also matter. Horses with dark coats make it harder to see the muscle tension and shadowing that define several of the grimace scale units. Breed-related differences in head shape can change how prominent certain muscles appear at rest, making the “strained” versus “normal” comparison trickier. The researchers who developed the enhanced version of the HGS have noted that some facial action units could benefit from more detailed anatomical descriptions to account for these variations, because a draft horse’s relaxed face and an Arabian’s relaxed face simply do not look the same.⁵

This does not mean facial scoring is unreliable across breeds. It means you need a baseline. Knowing what your individual horse looks like when it is comfortable, rested, and healthy gives you the reference point that makes deviations visible. If you have never paid close attention to your horse’s face during a calm moment in the pasture, you will have a harder time recognizing when something has shifted.

Beyond the Face: Body Signals That Travel With Pain

Facial expression is one channel of pain communication, but it rarely exists in isolation. Research comparing multiple equine pain scales found that body posture and physiological signs often accompany the facial changes. Posture shifts, such as a rigid stance, weight shifting, or guarding a limb, correlated with pain across several different scoring systems. Heart rate and body temperature changes also appeared in composite pain models alongside facial cues.⁶

In practice, this means the face is your early warning system, but the rest of the horse fills in the picture. A horse showing two or three facial pain units and also standing with an unusual posture, refusing to move freely, or showing changes in eating behavior is giving you a much louder signal than any one of those things alone. Colic is a classic example: the facial grimace often appears alongside pawing, looking at the flank, and changes in gut sounds. Musculoskeletal pain may pair the pain face with uneven movement or reluctance to pick up a particular lead.

Dental and Cranial Pain

Some types of pain produce particularly distinctive facial presentations because they directly involve the structures of the head. Dental problems, ear infections, and nerve-related conditions can cause asymmetric facial changes that look different from the bilateral grimace of body pain. A case report of a sport horse with middle ear infection, infraorbital canal malposition, and dental malocclusion documented a right-sided head tilt, ear drooping on the affected side, nostril asymmetry, and pronounced headshaking behavior.⁷

One-sided facial changes are a red flag that the pain source may be in the head itself. While the standard Horse Grimace Scale was developed primarily for body pain and tends to produce symmetric changes, head pain can break that symmetry. If you notice that one ear droops more than the other, one nostril looks different, or the horse consistently tilts or shakes its head to one side, dental or ear-related problems deserve investigation. These cases can be complex, with multiple overlapping issues contributing to the signs, and they often require imaging and specialist evaluation to untangle.

What to Do When You See the Pain Face

Recognizing the pain face is only useful if it changes what you do next. The appropriate response depends on the context and severity of what you are seeing.

If the signs appear suddenly and are accompanied by other distress signals like pawing, rolling, sweating, or changes in posture, you may be looking at colic or another acute abdominal problem. Remove access to food, keep the horse in a safe area where you can monitor it, and call a veterinarian. Colic can escalate quickly, and facial grimace scoring has been shown to be a reliable indicator in these situations.³

If you notice the pain face during or after riding, stop working the horse and note exactly what you saw. Document it if you can, ideally with photos or video of the face at rest for comparison. A veterinarian performing a lameness workup will benefit from knowing which facial changes you observed and under what conditions. Because pain scores improve when the underlying lameness is treated, persistent facial pain signals under saddle should prompt a veterinary evaluation rather than a training adjustment.⁴

For post-surgical horses, facial scoring gives you a way to monitor whether pain management is working. If a horse that received analgesics after castration or another procedure is still showing multiple grimace scale features several hours later, that information is worth communicating to the veterinarian. Pain protocols may need adjustment, and the face gives you earlier feedback than waiting for the horse to stop eating or become visibly depressed.

For chronic or subtle signs, the approach is different. A horse that consistently shows mild orbital tightening, slightly strained nostrils, or a tense chin may be dealing with low-grade discomfort that is easy to normalize over time. This is where baseline knowledge of your horse’s face becomes critical. Compare what you see today with what you remember from when the horse was last clearly comfortable. Chronic pain is harder to catch because the horse adapts, and so does the human watching it.

AI-Assisted Pain Detection

Researchers are actively working on automated systems that could read horse faces from photos or video, removing the subjectivity of human observation. Early results are encouraging. One deep-learning system achieved about 76% accuracy when classifying pain into three levels from images, and roughly 88% accuracy when the task was simplified to a binary question of pain present versus not present.⁸

Another line of research using recurrent neural networks on video footage has found that the dynamics of facial movement, not just still-frame snapshots, carry important pain information. These models, even with small datasets, outperformed human raters in classifying experimental pain.⁹ The technology is not ready for a barn-side app yet, but it points toward a future where continuous, objective pain monitoring could be part of routine horse management. Stall cameras feeding into a trained algorithm could, in theory, alert owners to early signs of colic or post-operative pain without anyone needing to be physically present.

How the Horse Fits Into the Broader Grimace Scale Picture

The idea of reading pain from an animal’s face is not unique to horses. Grimace scales now exist for mice, rats, rabbits, cats, sheep, pigs, cattle, ferrets, and donkeys.¹⁰ The horse version is among the most developed and validated, partly because horses have relatively expressive faces with large, mobile features that are easy to observe. The equine grimace scale has also benefited from a large body of research on specific clinical conditions like castration and colic that provide clear before-and-after comparisons.

That said, a systematic review of grimace scales across species found considerable variability in how these tools were developed and how thoroughly their measurement properties were tested.¹⁰ The horse scale is one of the stronger ones, but even it continues to be refined. Updated anatomical descriptions for each facial action unit have been proposed to improve consistency across different breeds and assessment conditions.⁵ The science is mature enough to be clinically useful right now, but it is still actively developing, which means the tools available to horse owners and veterinarians will likely keep getting better over the next several years.