You got hurt at work. A doctor examined you, wrote a report, and now the insurance company is telling you that a large part of your permanent disability is "pre-existing" — the result of aging, old injuries, or normal wear and tear. Your check looks smaller than you expected.
If this is happening to you, take a breath. The word "pre-existing" is not the same as a denial. It is the beginning of a legal argument, and that argument has rules.
In California, this process is called apportionment. Understanding how it works is the difference between accepting a number handed to you and knowing whether that number is actually correct.
What Apportionment Actually Means
Apportionment is how California divides your permanent disability between the work injury and other causes. It does not affect your medical treatment, and it does not reduce your temporary disability payments while you are recovering. It only applies to permanent disability — the lasting effect the injury leaves behind after your condition stabilizes.
The idea is straightforward on paper. If your permanent disability was caused entirely by your job, the employer is responsible for all of it. If part of that disability came from something unrelated to work, the employer is only responsible for the work-related share.
The problem is not the idea. The problem is how often the "other causes" share gets inflated.
The Two Laws That Control Your Award
Two sections of the California Labor Code drive nearly every apportionment dispute.
- Labor Code §4663 requires that apportionment be based on causation. When a physician evaluates your permanent disability, that doctor must address what caused it and, in a written report, state approximately what percentage was caused by the work injury and what percentage was caused by other factors — such as prior injuries, underlying degeneration, or non-industrial conditions.
- Labor Code §4664 limits the employer to the percentage of permanent disability that was actually caused by the work injury. It also allows a prior permanent disability award for the same body part to be subtracted from a later one.
Since 2004, when Senate Bill 899 reshaped this area of law, apportionment is "to causation." In plain terms, the question is no longer just how disabled you are — it is what caused the disability.
Why Insurers Lean So Hard on "Pre-Existing"
Here is where injured workers get hurt a second time. Because apportionment lowers what the insurer pays, there is a built-in incentive to attribute as much of your disability as possible to something other than your job.
The most common tactics you will see:
- Blaming ordinary aging or "degenerative changes" that show up on an MRI — even though almost everyone past a certain age has some degeneration whether or not it ever caused symptoms.
- Pointing to an old injury that had fully healed and never limited you before this incident.
- Assigning a percentage to "non-industrial factors" without explaining, in medical terms, how those factors actually produce the disability you have now.
A finding on an imaging study is not the same thing as a cause of disability. Many people walk around with degeneration on a scan and no pain and no limitations. The relevant question is what is causing your permanent disability today — not what a radiologist happens to notice.
An Apportionment Opinion Must Be Backed by Real Evidence
This is the part insurers hope you never learn. A doctor cannot simply announce a percentage. Under California law, an apportionment opinion is only valid if it is supported by substantial medical evidence.
That means the physician must do more than say the magic words. The doctor generally needs to:
- Explain what the "other" cause is, in medical terms.
- Explain how and why that cause is responsible for a specific portion of your permanent disability.
- Show reasoning that connects the medical facts of your case to the percentage assigned.
An opinion that just says "50% is due to pre-existing degeneration" with no medical explanation behind it is not substantial evidence. A poorly reasoned apportionment can be challenged — and when it is successfully challenged, that portion of the reduction can fall away.
How a Weak Apportionment Gets Challenged
You do not have to accept a doctor's percentage as final. There are established ways to push back within the workers' compensation system.
- The medical report can be examined closely to see whether it actually explains its reasoning or just states a conclusion.
- The evaluating physician can be questioned about the basis for the percentage.
- Where a report falls short of the legal standard, that shortcoming can be raised before a workers' compensation judge, who decides what weight the opinion deserves.
None of this is something you should have to navigate alone while you are also trying to heal. The rules are technical, the deadlines are real, and the insurer's doctors and lawyers do this every day.
Talk to Solov & Teitell Before You Accept a Reduced Number
If an apportionment opinion is shrinking your permanent disability, get it reviewed before you sign anything. A number that looks final on paper may rest on a medical report that does not meet California's legal standard.
The Law Offices of Solov & Teitell have represented injured California workers since 1965. From our Los Angeles office we serve clients in English, Spanish, and Korean, and we handle workers' compensation matters every day. You can get a rough sense of what your claim may be worth using our permanent disability calculator, and then contact us for a free consultation to have your report and your apportionment reviewed.
The consultation is free, and there is no fee unless we recover for you. If "pre-existing" is being used to cut your award, let us look at whether that reduction actually holds up.
This article is general information about California law and is not legal advice. For advice about your situation, consult a qualified attorney.