Physicians may use an evaluative process when determining an impairment rating

Colorado Revised Statute, § 8-42-101, subsections (3)(a)(I) and (3.7), states that in workers’ compensation cases, physical impairment ratings “shall be based on” the revised third edition of the American Medical Association’s Guides to the Evaluation of Permanent Impairment (AMA Guides).

In Fisher, the Colorado Court of Appeals (the Court) considered whether the phrase “shall be based on” bars a physician from using an evaluative process to determine an impairment rating that is not described in the AMA Guides.

The claimant sought review of a final order issued by the Industrial Claim Appeals Office (the Panel) that upheld the decision of the ALJ, who assigned the claimant a 13% scheduled impairment rating of the left knee. The claimant argued his impairment should have been higher and contested his authorized treating physician’s method of calculating the impairment rating. The physician used a method known as “normalization” where the doctor compares the range of motion of the claimant’s uninjured joint, with the range of motion of the claimant’s injured joint. The range of motion of the uninjured joint is considered to be the baseline. Once the physician obtains both range of motion measurements, he then subtracts any impairment to the range of motion of the uninjured joint from the impairment to the injured joint to reach the final impairment rating. The claimant argued that the phrase “shall be based on” means the physician cannot employ the process of normalization because it is not outlined in the AMA Guides.

In affirming the Panel’s order, the Court held the plain language of the statute did not bar a physician from using the method of normalization to calculate impairment. The Court stated that the phrase “shall be based on” means the AMA Guides serve as a starting point, and is not the exclusive source for determining an impairment rating. In reaching this conclusion, the Court found a few facts persuasive. First, doctors have been using the practice of normalization for at least a decade and second, it is outlined in the Impairment Rating Tips, a Desk Aid published by the Worker’s Compensation Division of the Department of Labor and Employment. Third, while the third edition of the AMA Guides does not address normalization, other editions of the Guides consider it reasonable. Fourth, the Impairment Rating Tips also express when normalization should not be used. Specifically a physician should not use normalization when the opposite joint has a known previous injury which may not reflect the “normal” range of motion for that individual. The claimant did not have a previous known injury to his right knee that would render the normalization method improper. Fifth, prior courts have already rejected numerous challenges to normalization and to the Impairment Rating Tips concluding normalization was a legitimate process that did not violate the statute. Lastly, the Court determined the Impairment Rating Tips are not contradictory to the statute and is consistent with the legislature’s intent to allow physicians discretion in calculating impairment. The Court explained the Impairment Rating Tips does not impose any mandates on how a doctor is to calculate an impairment rating, but rather provides guidance and discretion in calculating impairment. For these reasons, the Court upheld the Panel’s order affirming the ALJ’s decision.

Fisher v. Indus. Claim Appeals Office, 2021COA27 (Colo. Ct. App. Mar. 4, 2021).


Want to know more? Contact Karina Prigge at or 877-259-5693.

March 2021 Newsletter