Impairment in injury claims

In plain English: impairment is a doctor's measure of how much function a part of your body, or your body as a whole, has lost because of an injury. It is often expressed as a percentage.

Impairment is not the same as disability

Impairment is medical. Disability is practical. A pianist and a lawyer who lose the tip of the same finger have the same impairment rating, but only one has lost a career. Claims use both: the impairment rating gives a number insurers and courts can work with, and disability evidence shows what that number means in your life.

How ratings are usually done

In much of the US and Canada, doctors rate impairment using the American Medical Association's Guides to the Evaluation of Permanent Impairment. The examiner measures things like range of motion, strength, nerve function and imaging findings, then converts them into a whole-person percentage. Different editions of the Guides can give quite different numbers for the same injury, and states and workers' compensation boards choose which edition they use.

Ratings are normally given once you reach maximum medical improvement. Rating too early risks understating an injury that is still changing.

When the rating can make or break a claim

• Workers' compensation. Permanent partial disability payments are often calculated directly from the rating.
• US no-fault states. Some states only let you sue for pain and suffering if you meet a serious injury threshold. Michigan, for example, uses "serious impairment of body function", and New York lists categories of serious injury.
• Ontario. To sue for pain and suffering after a car crash, you generally need a permanent serious impairment of an important physical, mental or psychological function. The accident benefits system also has a "catastrophic impairment" category that opens the door to much higher benefits.
• UK claims. Percentage ratings are used less. Courts rely on expert reports and the Judicial College Guidelines, which describe injuries by severity and effect.

If you disagree with a rating

Ratings involve judgment. Ask for the report, check which edition of the Guides was used, and see whether every injured body part was assessed. Your own doctor or an independent medical opinion can challenge a low figure. Insurer-chosen examiners sometimes rate lower, so a second opinion is common in contested cases.

Next: permanent impairment · fault vs no-fault insurance · compensation.

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