Advances in mouse pain assessment tools are transforming laboratory animal welfare, enabling researchers to better detect and manage pain in one of the most widely used research animals in the world.
Mouse pain assessment has been transformed by the development and widespread adoption of the Mouse Grimace Scale. Before this tool, laboratory mice experiencing post-procedural or disease-related pain were often inadequately managed because pain was difficult to assess reliably. The MGS, which scores orbital tightening, nose bulge, cheek bulge, ear position, and whisker changes, provides a validated, non-invasive, and rapid method to assess pain state. Its adoption has revealed that many standard laboratory procedures — including injections, blood draws, and post-surgical recovery — produced more pain than previously recognized. Armed with this knowledge, research institutions have been able to refine analgesia protocols, improving welfare while also improving data quality, since pain is a significant confounding variable in behavioral and physiological research. Automated scoring using machine learning is now enabling continuous, unbiased monitoring that was previously impossible with manual observation alone.