Facial expressions of pain in cats: the development and validation of a Feline Grimace Scale

This study developed and validated the Feline Grimace Scale, a tool that assesses acute pain in cats by scoring facial action units such as ear position, orbital tightening, muzzle tension, whisker change, and head position. The researchers demonstrated that these facial features reliably reflect pain and respond to analgesic treatment, providing a practical, rapid, and validated method to recognize pain in a species notorious for hiding it. It matters because cats conceal pain, leading to under-recognition and undertreatment, and the Feline Grimace Scale gave clinicians and owners an objective, easy-to-use instrument to detect pain and assess analgesic efficacy, significantly advancing feline welfare and pain management by making pain assessment more accessible and reliable in both clinical and research settings.