Accurately assessing and managing pain in laboratory mice is a critical welfare challenge, and new tools including facial grimace scales have significantly improved the ability to detect and treat mouse pain.
Mouse pain assessment represents one of the most significant welfare refinements in laboratory animal science of the past two decades. Before the grimace scale and validated behavioral indicators, mouse pain was routinely underestimated because mice suppress pain behavior to avoid appearing vulnerable to predators. This evolutionary strategy masked significant post-procedural suffering. The availability of validated, easy-to-use assessment tools has transformed pain management practices — researchers who can reliably detect pain can also evaluate whether analgesic protocols are effective. This is the refinement principle in action: improving the welfare of animals within an experiment rather than eliminating the experiment. The challenge now is ensuring universal training in these tools and requiring their use in institutional protocols.