Impairment Ratings and the AMA Guides

Once your doctor says you have healed as much as you are going to heal, the next number that gets written down is the one that follows you for the rest of the claim: your permanent impairment rating. It is usually expressed as a percentage — “10% impairment of the right shoulder,” or “8% impairment of the whole person” — and in many states that percentage, more than anything else, drives the size of your permanent disability benefit. It is worth understanding where the number comes from, because it is less objective than it sounds, and it is very much worth double-checking.

One thing to say at the outset: workers' compensation is state law, and the rules on impairment ratings differ substantially from one state to the next — which manual is used, who gets to do the rating, how the percentage converts into money, and how long you have to object. This article explains the framework that is common across systems. For the specifics that actually govern your claim, go to your own state's workers' compensation agency, board, or commission. The U.S. Department of Labor maintains a directory of state workers' compensation officials.

The turning point: maximum medical improvement

Maximum medical improvement (MMI) is the pivot point of a workers' comp claim. It is the moment your doctor concludes that your condition has stabilized and that further treatment is not likely to meaningfully improve it. MMI does not mean you are healed, pain-free, or back to normal — only that the medical picture has plateaued.

MMI matters because it is where the claim shifts from temporary disability benefits (temporary total or temporary partial, paid while you are actively recovering and losing time or wages) to the question of permanent disability (permanent partial or, in the most serious cases, permanent total). And it is at MMI that a physician is typically asked to assign an impairment rating.

What an impairment rating actually measures

An impairment rating is a medical measurement. It is a doctor's attempt to quantify how much function a body part — or your body as a whole — has permanently lost, based on findings like range of motion, strength, sensation and nerve function, imaging, and the specific diagnosis.

It is not, standing alone, a statement about whether you can still do your job or earn a living. That distinction is the one workers most often get blindsided by, and we come back to it below.

Where the percentage comes from: the AMA Guides

To keep impairment ratings from being freehand guesswork, many states require physicians to follow a published reference manual: the American Medical Association's Guides to the Evaluation of Permanent Impairment. It is a large book of tables, clinical tests, and formulas that translates a diagnosis plus examination findings into a percentage. Some states use their own state-specific impairment schedule or rating system instead, and some blend the two. Which approach applies to you is set by your state's law — ask your state agency.

Here is the part that surprises many injured workers: the AMA has published several editions of the Guides over the decades, and they are not interchangeable. The methodology genuinely changed between editions. Beginning with the Sixth Edition, the AMA shifted from ratings built largely around measured clinical findings (including range-of-motion measurement for spine impairment) toward a diagnosis-based approach, in which the diagnosis sets the starting value and a limited set of adjustment factors moves it up or down.

That change was not cosmetic. The U.S. Department of Labor — which runs the separate federal workers' compensation program for civilian federal employees (FECA, administered by the Office of Workers' Compensation Programs) — has itself acknowledged that the move from the Fifth Edition to the Sixth reduced impairment compensation for some workers by amounts that were not anticipated. In January 2025 the agency briefly changed its procedures to allow either the Fifth or the Sixth Edition, then revoked that change and reinstated its prior practice of using a single edition. You do not need to follow that history to take the point from it: the edition is a legal choice, it is contested, and it can change the size of a rating for the exact same injury.

States do not all require the same edition. Some point to whatever edition is current; some have frozen their statute or regulation to an older edition; some use a homegrown system. Do not assume. Ask which edition or system your rating physician applied, and confirm with your state's workers' compensation agency that it is the one your state requires. A rating performed under the wrong manual is a legitimate basis to object.

Impairment versus disability: two different questions

This is the single most misunderstood concept in permanent workers' comp benefits.

• Impairment is a medical measure: what has been anatomically or functionally lost, expressed as a percentage of a body part or of the whole person.
• Disability is a legal and economic measure: what that loss means for your ability to work and earn, considering things like your age, education, job skills, and work history.

A 10% shoulder impairment means something very different for a working carpenter than for someone whose job never requires reaching overhead. States translate impairment into benefits in different ways:

• Some pay permanent partial disability strictly off the impairment percentage — through a fixed “schedule” that assigns a set value to each body part, or through a whole-person formula. Earning capacity, age, and education generally do not move the number.
• Others use a wage loss or loss of earning capacity approach, in which the rating is only a starting point and vocational factors get weighed in.
• Many states use a hybrid, routing certain “scheduled” injuries down one track and everything else down another.

Whichever track your state uses, the dollar value of a permanent award is almost always calculated off your average weekly wage — the earnings figure your benefit rate is built on. If your average weekly wage was calculated too low (for example, by leaving out overtime, a second job, or a short work history that does not reflect your real earnings, depending on your state's rules), that error quietly shrinks your permanent award too. It is worth checking alongside the rating.

Do not assume your benefit is simply “the percentage times a number you saw online.” Ask your state agency, or a workers' comp attorney, how your state actually converts a rating into an award.

Why the treating doctor's rating and the IME rating so often disagree

It is common for a treating physician's rating and the rating from an insurer-arranged independent medical examination (IME) to come out differently, sometimes by a wide margin. There are several honest reasons:

• Genuine medical judgment. Even a rigorous manual leaves room for judgment, particularly for hard-to-measure conditions like chronic pain, soft-tissue spine injuries, or psychological sequelae. Two careful, honest physicians can land in different places.
• Different information. The IME physician is often working from a single appointment and whatever records were forwarded. Your treating doctor has seen the whole arc of your recovery.
• Different manuals or methods. If one physician used a different edition, or used a range-of-motion method where the state requires a diagnosis-based one (or the reverse), the percentages will not match.
• Structural position. The IME physician is selected and paid by the insurance carrier; the treating physician has an ongoing relationship with you. Neither fact makes anyone dishonest, but each side's position is one reason comp systems build in a way to resolve the disagreement.

A gap between two ratings is a routine, expected dispute — not an accusation against anyone. Comp systems are built to resolve exactly this.

Getting a second rating

You are generally not stuck with a rating you believe is wrong. Depending on your state, the available routes commonly include:

• An independent or second rating examination, sometimes through a state-maintained panel, registry, or list of certified rating physicians;
• A second-opinion or rebuttal evaluation when the insurer's IME conflicts sharply with your treating doctor;
• A formal hearing before your state's workers' compensation board, commission, or judge, who decides which rating to credit if the parties cannot resolve it informally.

The exact mechanism, the forms, and who pays for the second exam all vary by state. Your state agency's claims office or ombudsman/information officer can walk you through the process at no charge, and this is the kind of dispute a workers' compensation attorney handles routinely — most consult for free.

Deadlines: short, state-specific, and full of exceptions

If you disagree with an MMI finding or an impairment rating, there is usually a window to object formally — and it is often short. How short varies enormously from state to state, so this article deliberately does not give you a number. Confirm your deadline with your state's workers' compensation agency, and do not rely on a figure you found on a general website. Missing an objection window can lock in a rating you believe is wrong. Treat this as urgent.

At the same time — and this matters just as much — do not assume you are too late just because time has passed. Deadlines in workers' comp very often come with escape hatches, and workers give up rights every year because nobody told them so. Exceptions that commonly exist include:

• The discovery rule. For conditions that develop over time — cumulative trauma, repetitive-strain injuries, occupational disease — the clock in many states starts not at first exposure but when you knew, or reasonably should have known, that you had the condition and that it was work-related. That can be far later than you assume.
• The right to reopen for a change in condition. Many states allow a closed claim to be reopened, or a new rating to be sought, if your condition materially worsens after the original rating. A rating is not always forever.
• Excused late notice. Where a notice deadline is at issue, many states will excuse a late report if the employer already knew about the injury, or if the employer or insurer was not actually prejudiced by the delay.
• Tolling. Time limits are often paused for minors or for a worker who was legally incapacitated.

Bottom line: do not walk away because you have concluded on your own that the door is closed. Call your state agency, or a workers' compensation attorney — most offer a free consultation — and ask specifically whether any of these exceptions apply to you before you give up.

What to do if you disagree with your impairment rating

1. Get a full copy of the rating report, including which manual and which edition (or state-specific system) was applied.
2. Ask the rating physician, in writing, to explain how the number was reached and which tables were used.
3. Contact your state workers' compensation agency to confirm (a) the edition or system your state requires, (b) your deadline to object, and (c) the procedure.
4. Check your average weekly wage while you are at it — an understated wage shrinks the award no matter how good the rating is.
5. Request a second opinion or independent rating exam through your state's process.
6. If the ratings still conflict, ask about a hearing before your state's board, commission, or judge, and talk to a workers' compensation attorney — most consult for free, and many state agencies also offer a free ombudsman or information officer.

What an impairment rating does not decide

A few boundaries worth keeping straight:

• Your comp impairment rating does not determine Social Security disability (SSDI or SSI). Those are federal programs with an entirely different standard, decided by a different agency.
• It is separate from any third-party claim against someone other than your employer who negligently caused your injury — a defective machine's manufacturer, a driver who hit you on the job. Workers' comp is generally your exclusive remedy against your employer, but that bargain does not shield a negligent third party. Note that if you recover from a third party, the comp insurer will usually assert a lien (subrogation) against that recovery for what it paid out.
• If you are a federal civilian employee (FECA), a maritime worker (Longshore or the Jones Act), or a railroad worker (FELA), you are in a separate system with its own rules — and the Jones Act and FELA are fault-based, meaning negligence must be shown, unlike the no-fault state comp systems. Do not apply this article's state-comp framework to those claims without checking.

Frequently asked questions

Does a higher impairment percentage always mean more money?

Generally yes, but how much more depends entirely on your state's formula — and in some states your age, education, and work history also affect the final award. Your average weekly wage is usually part of the calculation too. Ask your state agency how the conversion works in your state.

Can I choose my own doctor to do the rating?

It depends on your state. Who chooses the treating physician — you, the employer, or the insurer — is itself a state-by-state rule, and the treating physician usually does the first rating. Many states also give you a route to an independent evaluation if you disagree. Check your specific rights with your state agency.

What if my condition gets worse after I'm rated?

Many states let you reopen a claim or seek a new rating if your condition materially worsens after the original rating. This is a real and common exception to “the case is closed,” and it has its own time limits that vary by state. Ask your state agency about its reopening rules rather than assuming you are stuck.

Is an impairment rating the same as being found “disabled” for Social Security?

No. Workers' comp impairment ratings and Social Security disability determinations use completely different standards and are decided by different agencies. A modest comp rating does not mean you cannot qualify for SSDI, and a high one does not guarantee you will.

The insurer's IME doctor gave a much lower rating than my doctor. Is that fraud?

Not necessarily, and you should not assume so. Differences in medical judgment are common, especially for conditions that are hard to measure, and two physicians can apply the manual honestly and still disagree. Sometimes the gap simply comes from different information or a different edition of the Guides. A sharp, unexplained gap is exactly what the second-opinion and hearing processes exist to resolve — use them.

Does it matter which edition of the AMA Guides was used?

It can matter a great deal. The editions use different methodologies, and the same injury can produce a different percentage under different editions. Your state specifies which edition or system applies. If your rating was done under the wrong one, that is a legitimate ground to challenge it — confirm the requirement with your state agency.

This article provides general information about how workers' compensation systems typically work. It is not legal advice and does not create an attorney-client relationship. Workers' compensation is state law and varies significantly from state to state — contact your state's workers' compensation agency, board, or commission, or a workers' compensation attorney, about your specific situation.