Apportionment: When They Blame Your Prior Injury

Apportionment is the argument an insurer makes when it says it should only pay for part of your permanent disability because some of it, in its view, comes from an old injury, a pre-existing condition, or ordinary wear and tear rather than from the job. It does not erase your claim, and it does not mean you get nothing. But it can shrink a permanent disability award, and it is one of the most common and most misunderstood disputes in workers' compensation, especially for workers with any prior medical history at all.

If an adjuster, an independent medical examiner, or a defense letter has used the words "apportionment," "pre-existing," or "degenerative" about your case, take a breath. This is a normal and expected part of many claims that reach a permanent disability rating. Filing a comp claim is not suing anyone; it is claiming a benefit that exists precisely because you got hurt at work. Apportionment is a dispute about the size of that benefit, and it is very often answerable with the right medical evidence.

One thing to know at the outset: workers' compensation is a no-fault system. Apportionment is not about blaming you, and it is not a finding that you did anything wrong. It is an accounting question about how much of your permanent impairment the work injury is responsible for.

The starting rule: the employer takes the worker as it finds them

Before you worry about apportionment, understand the baseline that most states start from. Workers' compensation generally follows what is sometimes called the "eggshell" or "as you find them" principle: your employer takes you as you are, prior conditions and all. If work aggravates, accelerates, combines with, or lights up a pre-existing condition into an actual disability, that resulting disability is generally compensable, even if you had no symptoms before, and even if a healthier coworker might not have been hurt by the same task.

In plain terms: a bad back that never bothered you, that a work injury now makes disabling, is generally a comp case in most states. You do not have to have been in perfect health before you got hurt. That principle is why workers with old injuries, arthritis, prior surgeries, or degenerative disc disease can still bring an honest, legitimate claim when work makes things worse.

Like nearly everything in comp, this varies. Workers' compensation is state law, and there are more than fifty separate systems. Confirm how your state treats aggravation of a pre-existing condition with your state's workers' compensation agency, board, or commission. The U.S. Department of Labor maintains a directory of state workers' compensation officials if you are not sure which agency covers you.

Then comes the carve-back: apportionment

Apportionment is the mechanism used to divide up a permanent disability once it is time to rate it. That generally happens at or after maximum medical improvement, the point at which your condition has stabilized and is not expected to improve much further, which is also the pivot from temporary wage benefits to permanent disability benefits. The theory behind apportionment is that if part of your permanent impairment truly existed before this injury, the current employer's insurer should not have to pay for that share. Benefits are then split, often on a percentage basis, between what this injury caused and what was supposedly already there.

Apportionment is normally aimed at the permanent disability rating. It is not, by itself, a basis to cut off medical treatment for a work injury, though insurers dispute medical care through other channels such as utilization review.

This is where state law diverges sharply, and the differences matter enormously to how much of an award survives. Broadly, and with the caution that the exact legal test is set by each state's statutes and case law:

• Narrower approaches allow apportionment only to a prior condition that was already meaningfully disabling, for example one that was symptomatic and limiting, that had already been rated as a permanent impairment, or that had already been compensated in an earlier award. Under this approach, an old condition that never limited you and never produced a rating generally cannot be used to reduce your award just because it appears somewhere in your medical records.
• Broader approaches allow apportionment to pre-existing pathology that a doctor identifies as contributing to the current disability, even if it was never diagnosed, never treated, never rated, and never cost you a day of work.
• Some states apportion sparingly, staying closer to the traditional rule that the employer takes the worker as it finds them.

Because that gap is so wide, you need to find out how your state handles apportionment. Ask your state workers' compensation agency or a workers' comp attorney which approach applies to your claim. Do not assume that a general description, including this one, matches your state's rule.

The evidence fight: old imaging, old claims, old chart notes

Once apportionment is on the table, the case becomes a records fight as much as a medical one. Expect the insurer's side to look for:

• Old imaging of the same body part, sometimes from years earlier, mentioning arthritis, disc bulges, or degeneration.
• Prior workers' comp or injury claims involving the same area of the body.
• Old chiropractic, physical therapy, or primary care notes mentioning back pain, neck stiffness, or similar complaints, even a single visit long ago.
• Your recorded statement or intake paperwork, read closely for anything that sounds like an admission of prior symptoms.

None of that is improper for an insurer to gather, and you should never hide or minimize your real history when asked about it. Concealing a prior injury or condition can be used to attack your credibility or to deny the claim for misrepresentation, and workers' compensation fraud is prosecuted. The better and the only lawful strategy is complete honesty paired with strong medical evidence explaining the difference between your old baseline and your new disability.

Why "degenerative changes" gets used against so many people

Here is what makes this defense so common: phrases like "degenerative changes," "degenerative disc disease," "spondylosis," and "age-related changes" appear on a very large share of spine, shoulder, and knee imaging, including in people who have never had a symptom. Published systematic reviews of imaging in asymptomatic adults, that is, people with no pain at all, find degenerative disc findings in a substantial and steadily rising share of people as age increases (see, for example, the systematic review of imaging features of spinal degeneration in asymptomatic populations in the NIH National Library of Medicine's PubMed Central). A radiologist describing degeneration is describing tissue, not making a legal finding about disability.

So a bare imaging report showing "moderate degenerative changes" is not proof that you were disabled before your work injury, even though it is sometimes waved around as if it were. Degeneration on a scan is not the same thing as a symptomatic, work-limiting, rated disability. The real question is never "does the imaging show wear and tear?" It is "did the work injury cause a new, measurable disability on top of whatever was already there, symptomatic or not?"

What a strong treating-doctor opinion actually has to say

Apportionment disputes usually turn on the quality of one document: the written opinion of your treating or evaluating physician. A weak report notes "degenerative changes present" and moves on. A report that holds up needs to:

• State clearly whether the pre-existing condition was actually causing disability, restrictions, or lost work time before this injury, or was silent and asymptomatic.
• Explain, in medical terms, how the work injury changed the condition, whether by aggravation, acceleration, or a new injury superimposed on old pathology, rather than merely noting that both exist.
• Address, to the extent the doctor reasonably can and consistent with your state's legal standard, what portion of the current disability is attributable to the work event versus a genuinely pre-existing, already-disabling condition, supported by medical reasoning rather than a reflexive percentage.
• Speak to your actual function and work history before the injury, not just what a scan shows. Imaging alone cannot establish that you were disabled if you were working full duty with no restrictions the day before you were hurt.

Apportionment findings that are not grounded in real medical reasoning, that simply point at an image and assign a number, are frequently open to challenge. If your doctor's report does not do this work, ask for clarification, and ask a workers' comp attorney whether a second opinion or a formal evaluation in your state's system could help.

The doctors in the middle: IMEs and evaluations

Insurers commonly send workers to an independent medical examination (IME), a one-time exam by a physician who is not your treating doctor and who is typically selected and paid by the insurer. IME reports are a frequent source of apportionment opinions, and an IME doctor who has seen you once is often the one assigning a percentage to an old condition.

Whether, and how, you can obtain a competing evaluation is entirely a matter of state procedure. Some states let a worker obtain their own evaluation, some appoint a neutral or state-selected evaluator, and some tightly restrict the choice of physicians. Ask your state's agency, or a comp attorney, what the mechanism is in your state before you agree that an IME's apportionment percentage is the last word.

Second-injury funds: the older policy answer

Long before apportionment became the standard battleground, states created second-injury funds (also called subsequent-injury funds) to solve a related problem: employers were reluctant to hire workers with a known prior injury or disability, fearing that a new work injury combining with an old one would leave them liable for a much larger combined disability. A second-injury fund lets the employer's insurer pay for the new injury's share while the fund, financed across the insurance system rather than by any single employer, covers the extra disability created by the combination.

The point was to encourage employers to hire people with disabilities and prior injuries instead of screening them out. Over the past few decades, however, many states have narrowed, capped, or closed their second-injury funds to new claims, and some funds now exist only to pay out claims from injuries that happened before a cutoff date. Whether your state still has an active fund, and whether it could apply to you, is something to ask your state workers' compensation agency directly. Do not assume it either way.

What to do if apportionment comes up in your claim

1. Be completely honest about your medical history with every doctor, in every recorded statement, and on every form. Never hide or minimize a prior injury. Honesty is both the right thing and the strategically stronger position.
2. Gather your own records: prior imaging, prior claims, and treatment notes, so nothing blindsides you and so your doctor has the full picture.
3. Ask your treating doctor to address apportionment in writing: what changed, what is new, and why, not just what the scan shows.
4. Do not accept a bare "degenerative changes" citation as the final word. Ask what evidence shows you were actually disabled before the injury, as opposed to merely having findings on an image.
5. Ask what evaluation rights you have if you disagree with an IME or insurance doctor's apportionment opinion. The procedure varies by state.
6. Ask about your state's second-injury or subsequent-injury fund and whether it still applies to claims like yours.
7. Watch every deadline. The time to dispute a rating, request a hearing, or appeal a decision is typically short, and it varies by state and by the stage of the case. Contact your state's workers' compensation agency the moment you receive a rating, denial, or apportionment finding you disagree with. Do not wait to see whether it resolves on its own.

Do not assume you are too late

Apportionment often surfaces late in a claim, well after the injury was first reported, when permanent disability is finally being rated. That timing can make people assume they have missed their window to push back. Deadlines in comp are real and they are short, but they are also full of exceptions, and this is where workers most often give up when they did not have to.

In many states, exceptions include: a discovery rule that can start certain clocks when you knew or reasonably should have known a condition was work-related, which matters enormously for cumulative trauma and occupational disease, where there is no single accident date; late notice being excused where the employer already knew about the injury or was not prejudiced by the delay; the right to reopen a claim for a change in condition; and tolling for minors or for a worker who was incapacitated. None of these apply automatically, and none of them substitute for checking the actual rule in your state.

If you are not sure whether you are within your deadline, do not guess and do not give up. Contact your state's workers' compensation agency or board, which usually has an ombudsman or information officer who answers worker questions at no charge, or talk to a workers' comp attorney. Many offer a free initial consultation. Finding out where you actually stand generally costs you nothing.

Where to get help

• Your state's workers' compensation agency, board, or commission. The U.S. Department of Labor lists state workers' compensation officials for every state.
• If you are a federal employee, a maritime or harbor worker, or a coal miner, you are in a separate system, not your state's. The DOL Office of Workers' Compensation Programs administers those programs. Railroad workers and seamen are in different systems again, and unlike state comp, those are fault-based.
• If your concern is job discrimination or retaliation rather than benefits, the U.S. Equal Employment Opportunity Commission handles disability discrimination charges, and your state labor agency may handle retaliation for filing a comp claim.

This article provides general legal information, not legal advice, and does not create an attorney-client relationship. Workers' compensation law differs in every state; check your state's rules with its workers' compensation agency or a licensed attorney in your state.