The most reliable indicators were stiffly backward ears, orbital tightening, tension above eye area, and prominent strained chewing muscles. | Photo: iStock

Horses show facial expressions that express pain, and researchers have used those expressions to create the horse grimace scale (HGS). While scientists know through the HGS that certain combinations of facial features can suggest pain, they wanted to determine which ones are most related to pain or are most reliable and consistently evaluated among clinicians.

So Emanuela Dalla Costa, DVM, PhD, Dipl. ECAWBM, of the Università degli Studi di Milano Department of Veterinary Medicine, in Milan, Italy, and colleagues set out to fill those knowledge gaps.

“Without an effective tool of assessing pain (a validated scale for pain assessment), we cannot identify when pain occurs, assess its severity, or assess the effectiveness of anything we do to treat the pain (such as analgesic medicines),” she said. “So, in our opinion, it is paramount not only to develop such a tool but also to test its scientific validity in order to be sure that what we are measuring is pain