Impairment Ratings in Workers' Comp: How They Work and Why They Matter
By the Empower Clinical Team
When an injured worker reaches maximum medical improvement and some lasting effect of the injury remains, most workers' compensation systems require a permanent impairment rating: a percentage that expresses how much the injury has permanently reduced the function of a body part or the body as a whole.
That percentage feeds directly into benefit calculations, which is why disputed ratings are among the most common friction points in a claim.
Where the numbers come from
Most jurisdictions base ratings on an edition of the AMA Guides to the Evaluation of Permanent Impairment, though which edition applies varies by state and claim date. The Guides give evaluators standardized methods: range-of-motion measurements, diagnosis-based estimates, and specific criteria for psychological conditions.
Two evaluators applying the same edition to the same worker should land close together. When ratings diverge widely, the cause is usually methodology: measurements not taken as specified, the wrong edition applied, or conclusions asserted without the required supporting findings.
What makes a rating defensible
A defensible rating shows its work. It identifies the edition and tables used, records the measurements behind every number, explains how apportionment was handled when prior conditions exist, and ties the final percentage to the criteria step by step.
Ratings that state a percentage without that trail invite an independent review, a second rating, and months of added dispute. The cost of a rushed rating is rarely visible until it is challenged.
Empower's standard
Empower evaluators document ratings so that any reader can reproduce the reasoning from the report alone. That transparency serves every party: workers get ratings grounded in evidence, and employers and carriers get numbers they can rely on in negotiation or hearing.
