Facial expressions of pain in cats: the Feline Grimace Scale

Evangelista and colleagues developed and validated a Feline Grimace Scale, a practical tool to assess acute pain in cats from facial expression. By analyzing photographs of cats in pain and after analgesia, they identified five facial action units that reliably change with pain: ear position, orbital tightening, muzzle tension, whisker position and head position. Observers scored each unit, and the resulting scale showed good reliability between raters, responsiveness to pain relief, and the ability to discriminate painful from comfortable cats, with a threshold score indicating likely need for analgesia. The grimace scale gives clinicians and caregivers an objective, quick way to recognize feline pain, which cats notoriously mask, improving welfare by enabling earlier and better-targeted treatment. It has become a widely adopted instrument in feline pain management.