People often mix up an impairment rating with a disability rating, and that confusion causes bad advice. An impairment rating is a medical opinion about how much permanent physical or mental function has been lost after an injury. A disability rating, by contrast, is the legal or benefits-related measure of how that loss affects someone's ability to work or live normally. One is mainly medical; the other is about real-world impact.

That difference matters because a percentage on a doctor's report is not automatic proof of what a claim is worth. After treatment ends and a person reaches maximum medical improvement, a physician may assign an impairment rating based on lasting damage to a body part or the body as a whole. People hear "10%" or "20%" and assume there is a fixed payout. Usually, it is not that simple.

In Missouri, impairment ratings often show up in workers' compensation cases, but benefits are not always controlled by the rating alone. Under Missouri Workers' Compensation Law, Chapter 287, the state looks at permanent partial disability or total disability, along with the facts of the injury and work limits. That matters after major disasters or jobsite injuries alike, including catastrophic trauma seen after events like the 2011 Joplin tornado. A low rating can still hide serious work problems, and a high rating does not guarantee a large award.