Grimace scales developed for mice, rats, rabbits, and other species enable reliable pain assessment by trained observers, transforming laboratory animal pain management from subjective impression to evidence-based practice.
The development of grimace scales for laboratory animals has been one of the most practically impactful advances in animal welfare science of the past two decades. Before these tools, pain assessment in laboratory animals relied on behavioral observation that was unreliable, inconsistent, and often missed subtle pain. Grimace scales provide a validated, objective, and teachable method that has demonstrated in multiple studies that standard laboratory procedures cause more pain than previously appreciated. Mandatory grimace scale training and post-procedure assessment represents an achievable refinement that could substantially reduce unrecognized pain in millions of research animals.