Identifying when a horse is in pain can be challenging. Firstly, horses are prey animals and as such, they have mechanisms in place which minimise any displays of pain . Secondly, horses don’t communicate in the same way we do so while they might tell us they are in pain we don’t often understand them until the pain gets worse or until it turns into a behavioural problem.
In 2015 Katrina Gleerup and associates  conducted a study on the facial expressions that horses have in reaction to pain. The researchers used the composite measure pain scale to analyse the horse’s behavioural changes and facial expressions . Gleerup and associates found 3 major areas on the horse’s face that can be used as indicators for pain:
Using this study, massage therapists, veterinarians, farriers, dentists, other equine specialists and owners are now able to identify when their horse may be in pain and therefore be able to resolve the issue while it is still small. Gleerup and associates aren’t the only ones who have researched the identification of pain within the horse. Many researchers have created pain scales that aid in determining the pain levels of horses for a range of issues such as colic, castration, musculoskeletal pain, and after surgery . In the papers that analyse facial features for pain indicators, they mostly agree on the same features listed above. Unfortunately, I don’t have all the pain indicators from the many research papers listed here, however, if you are interested in an overview, I suggest looking at the van Loon and van Dierendonck paper listed in the references .
Lameness is commonly used by horse owners to find tissue damage within their horse, the more lameness the horse presents with, the more damage there is likely to be. However, a recent study conducted by Carrie Ijichi and associates  found that there was no correlation between lameness and the severity of the injury. Instead, they found that the horse’s personality had a larger influence over how lame the horse appeared .
Horses with neurotic tendencies were found to be less tolerant to pain and therefore are more likely to show signs of serious lameness for less severe injuries . While this seems bad, neurotic horses are more likely to get treatment sooner due to their over-reaction and are more likely to reduce movement in the lame area for fear of re-injury . They also found that extroverted horses were more likely to display lameness rather than introverted horses, who may hide their suffering .
In conclusion, it can be difficult to identify whether your horse is experiencing any pain, however, analysis of your horse’s facial expressions may aid in the early identification of future problems. It is also important that you know the personality of your horse, as they may try to hide their symptoms or exaggerate the pain they are in.
 Taylor, P.M, Pascoe, P.J & Mama, K.R 2002, ‘Diagnosing and treating pain in the horse. Where are we today?’, The Veterinary Clinics: Equine Practice, vol. 18, pp. 1 – 19
 Gleerup, K, Forkman, B, Lindegaard, C & Anderson, P 2015, ‘An equine pain face’, Veterinary Anaesthesia and Analgesia, vol. 42, pp. 103 – 114
 van Loon, J.P.A.M & van Dierendonck, M.C 2018, ‘Objective pain assessment in horses’, The veterinary journal, vol. 242, pp. 1 – 7
 Ijichi, C, Collins, L & Elwood, R 2014, ‘Pain expression is linked to personality in horses’, Applied Animal Behaviour Science, vol. 152, pp. 38 – 43