Small Changes, Important Signals: Understanding the Horse Grimace Scale

Many horse owners ask themselves, how do I know if my horse is in pain? Subtle facial changes are often one of the earliest signs of discomfort, and learning to recognise these signs can make a significant difference.

As I am writing this, my pony Pasta is in the clinic. As an owner, this is an emotionally challenging time, and as a professional, I find myself constantly observing, looking for small, subtle changes that might indicate she is starting to feel better.

During my studies in Equine Physiotherapy in Germany and Equine Business Management in the Netherlands, we were taught to use the Horse Grimace Scale, HGS, a scientific tool developed by

Costa et al. in 2014. Originally designed to assess pain following castration procedures, the HGS has since become a valuable tool in broader equine pain assessment.

As both an equine professional and a private horse owner, I use the HGS regularly to gain initial insight into how horses are feeling. One of its strengths is that it allows us to observe the horse without intervening. We can assess facial expression before approaching or handling the horse, reducing the risk of influencing their response.

Understanding your horse’s current state is crucial. Small changes can be important signals that something may not be quite right.

The Six Facial Indicators of the Horse Grimace Scale

Example of a horse showing all six indicators of the Horse Grimace Scale at a pronounced level.

Notice the narrowed eye, visible tension above the orbit, defined chewing muscles, strained mouth, and elongated nostrils.

The HGS evaluates six specific facial action units:

1. Ear position, often pinned or held stiffly back

2. Orbital tightening, tension around the eye

3. Tension above the eyes

4. Tightened chewing muscles

5. Strained mouth and pronounced chin

6. Strained nostrils and flattening of the profile

Each indicator is scored as follows:

0 = not present

1 = moderately present

2 = obviously present

The combined score gives an indication of possible discomfort.

Observing your horse’s facial expression on a daily basis does not replace veterinary diagnosis, but it does empower you. It helps you notice patterns and recognize when something changes.

Early awareness allows for earlier conversations with professionals and can support more timely intervention.

Have you noticed any of these facial signs in your own horse?

If you are based in Utrecht or elsewhere in the Netherlands and would like a professional opinion, you are always welcome to reach out. In my neuromyoskeletal therapy sessions, we look at the whole horse, combining movement assessment and subtle pain indicators to understand what may be going on.

Sometimes a second set of eyes can bring reassurance, sometimes it brings clarity. Either way, you do not have to figure it out alone.

Sources

Costa, E. D., Minero, M., Lebelt, D., Stucke, D., Canali, E., & Leach, M. C. (2014). Development of the Horse Grimace Scale (HGS) as a pain assessment tool in horses undergoing routine castration. PLoS ONE, 9(3), e92281. https://doi.org/10.1371/journal.pone.0092281