MEDICAL FRONT
• A better way to read the signs
of lameness
• PPID diagnostic technique
advances
• Modern problem for an
ancient breed
• Wireless capsule camera
technology shows promise • Busting myths about gender
and coat color
• Good news about recovery
from colic surgery
Equine lameness can be difficult to detect, but a study from England confirms the reliability of a relatively new tool for identifying subtle signs of musculoskeletal pain in horses.
Developed at the Animal Health Trust in Newmarket in 2018, the Ridden Horse Pain Ethogram (RHpE) is a compilation of 24 behaviors, such as “head tilting,” “tail swishing” and “spontaneous changes of gait,” that have been proven to correlate with musculoskeletal pain (see “A System for Identifying Lameness,” opposite). If a horse exhibits eight or more of the behaviors, chances are good he is lame.
Undiagnosed lameness has a far-reaching impact on the lives of horses and their riders, says Sue Dyson, VetMB, PhD. “One of the reasons I was incentivized to develop a RHpE was I had become so dispirited by seeing so many horses who clearly had pain-related problems that had been ignored for far too long,” she explains. “The horse, the rider, the training technique were being blamed over and over again. Coercive training techniques were being used. Longer whips, spurs, tighter nosebands, ‘stronger’ bits were being employed. Moreover, veterinarians did not understand what they were looking at either ---if an enlightened owner sought advice, and there was no obvious lameness seen in hand, they were told that the horse had behavioral problems.”
In early research, most of the behaviors on the RHpE were found to be 10 times more likely to be seen in lame horses, and they were eliminated by measures that relieved pain---such as nerve blocks---which verified their association with discomfort.
For the most recent study, researchers selected 60 horses considered sound by their owners. The average age of the horses was 11 and they were used in a variety of English disciplines. Eleven were lesson horses at a riding school.
At the beginning of the study period, the horses were examined by a physiotherapist for signs of back pain. A master saddle fitter then checked the fit of each horse’s tack to determine if it could be a source of pain. Each horse was then ridden by his usual
rider through a dressagetype test that included walking, trotting, cantering and circling in both directions. An experienced veterinarian observed each ridden test and evaluated the horse for lameness, assigning a score on a 0-to-8 scale. The tests were also videotaped from two angles.
Next, a second researcher, unfamiliar with each horse’s lameness score, analyzed the videotapes, documenting any instances of the behaviors listed in the RHpE. Finally, a third researcher watched the videotapes and scored each rider’s skill on a scale of 1 to 10.
The combined data showed that the presence of eight or more behaviors listed on the RHpE correlated with a lameness diagnosis by the veterinarian who observed the ridden test---confirming the findings of the earlier research. The behaviors that had the strongest statistical correlation with lameness were ears being pinned back for five seconds or more, an intense stare for five seconds or more and repeated stumbling or dragging of both hind toes.
The researchers also found that almost threequarters of the horses (73 percent) that were assumed to be sound by their owners actually had some degree of lameness. Dyson says this result isn’t particularly