Pre-existing conditions and your claim

A prior injury to the same body part does not end your claim. It changes what you are claiming for, and it raises the bar on proof. Firms know this, which is why they ask about your history early.

Aggravation is compensable

California law is clear that you can recover when a negligent act makes a pre-existing condition worse. The claim is for the aggravation — the new or increased symptoms, the accelerated decline, the care you now need that you did not need before — not for the underlying condition itself.

Sources: CACI No. 3927 (aggravation of a pre-existing condition or disability), Judicial Council of California Civil Jury Instructions (2026 edition).

The eggshell-plaintiff principle

A defendant takes the plaintiff as they find them. If a prior condition made you more fragile, and the defendant's negligence caused you serious harm that a healthier person might have shrugged off, the defendant is still responsible for the harm actually caused. Vulnerability is not a discount.

Sources: CACI No. 3928 (unusually susceptible plaintiff).

Apportionment: where the fight is

The insurer's move is to say your current problems are just your old condition continuing on its natural course. Your side has to separate the two: what were you actually doing before the incident, what changed after, and what do the treating providers and imaging show. This is a medical question that turns on records and expert opinion, and it is the reason these cases need a complete, honest history from the start.

Degenerative findings on imaging

Many adults have disc bulges, arthritis, or other degenerative findings on an MRI and no symptoms at all. When one of those findings shows up after a crash, the insurer calls it "pre-existing and unrelated." The response is the timeline: no pain and full function before, specific new symptoms immediately after, consistent treatment since. The scan is not the case; the change in function is.

What helps

• Tell your lawyer and your doctors about every prior injury to the area, even old ones. Disclose it before the other side finds it.
• Gather your prior records so the "before" picture is concrete, not a guess.
• Be precise about what changed — activities you stopped, help you now need, work you cannot do.
• Keep treating consistently, so the "after" record is complete — how gaps in treatment affect a claim.

Common questions

Can I still bring a claim if I had a prior injury to the same body part?

Yes. California law lets you recover for making a pre-existing condition worse. What you recover for is the aggravation — the added harm — not the condition you already had (CACI No. 3927).

What is the "eggshell plaintiff" rule?

A defendant takes the injured person as they find them. If you were more vulnerable to injury because of a prior condition, the defendant is still responsible for the full harm their negligence caused, even if a healthier person would have been hurt less.

Will the insurer find out about my medical history?

Almost certainly. Once you make a claim, your relevant prior records are discoverable. Undisclosed prior injuries that surface later damage credibility far more than the prior injury itself.

What is apportionment?

Dividing the current symptoms between what the incident caused and what the prior condition would have caused anyway. It takes medical opinion, and it is where these cases are usually won or lost.