If a horse shows only one or two of these traits whilst being ridden, a musculoskeletal problem cannot be assumed. However, if eight or more of the 24 behavioural characteristics listed above are identified in a ridden horse, the likelihood that this horse is in pain during ridden exercise is high. Their studies showed that lame horses had on average nine of the above traits displayed when ridden versus an average of only two traits when they were not lame.
To follow this through further, some horses that displayed high RHPE scores (meaning they were suspected of having underlying lameness issues), were nerve-blocked to abolish pain and, when reassessed, their RHPE score was lower. Assessing these behavioural traits and relating them to performance in a three-day event (horses were assessed in the dressage warm-up and their performance in the cross-country leg compared) also showed a correlation between high RHPE scores and failure to complete the course.
Assessing the horses for these behaviours can be done live or by using a video recording of the horse. If assessed via video, the video must include observations of the horse being ridden from all sides (front back and to the side). Depending on the type of musculoskeletal discomfort felt by the horse, it may need to perform different levels of physically demanding work to identify whether these behavioural traits are expressed. At a minimum, horses do need to be assessed at the trot, canter, and performing transitions in straight lines and on circles (10-metre diameter). Not all horses that are lame will display these behaviours but the value of this test should be in identifying horses that are in discomfort and not showing overt lameness.
There are many other well-proven ways to diagnose overt lameness. When assessing these horses, other factors may need to be taken into consideration including anatomical features, the surface the horse is ridden on, the skill of the rider and the type of bit worn by the horse, as these can confuse the results by inducing observations not related to pain. Anatomical anomalies such as a residual head tilt from a previous trauma that occurred many years prior should not be misinterpreted as a sign of pain. These types of anatomical differences should be noted prior to the horse being ridden and not used as a marker of behavioural change. Horses worked on a poorly maintained surface or on irregular ground should not be assessed as being lame because they stumble or trip.
The observations and the interpretation of the listed 24 characteristics will be improved and be more repeatable if the person assessing the horse is familiarised with the ethogram and aware of the defining characteristics of the behaviours. Training is available online (Dyson S. 2019 How to recognise the 24 behaviors indicating pain in the ridden horse.)