Preexisting Conditions Don't Kill Your Injury Claim

Why the law lets you recover even if a crash worsened an old injury, and how insurers try to use your history against you anyway.

If you had back pain, a bad knee, arthritis, or an old injury before your crash, you've probably already heard an insurance adjuster mention it. That's not an accident. Pointing to your medical history is one of the fastest ways an insurer can try to shrink or deny a claim, by arguing your current pain was already there and has nothing to do with what just happened to you.

But the law doesn't work the way insurers want you to think. There's a long-standing legal principle, sometimes called the eggshell plaintiff rule, that says a person who causes harm has to take the injured person as they find them. If a condition you already had made this crash hurt you more than it would have hurt someone else, the at-fault driver is still responsible for that extra harm. This article explains how that rule actually works and what it takes to use it.

What the eggshell plaintiff rule actually means

The name comes from an old example: if someone has a skull as fragile as an eggshell and a minor blow shatters it, the person who caused the blow doesn't get a pass just because a healthier person would have only gotten a bruise. The rule applies the same way to any preexisting condition, not just unusual or rare ones. Degenerative disc disease, prior surgeries, old fractures, arthritis, and even prior injuries from a past crash all count.

In practice, this means the at-fault driver or their insurer can't argue 'you were already fragile, so we owe you less than a healthy person would get.' The legal question isn't whether you were perfectly healthy before. It's whether the crash made your condition worse, caused new symptoms, or sped up a decline you weren't otherwise facing. If it did, that worsening is compensable, even if the underlying condition was there for years.

Aggravation versus a new injury: why the difference matters

Claims involving preexisting conditions usually come down to one medical question: did the crash aggravate an existing condition, or cause a separate, new injury on top of it? Both are valid claims, but they get proven differently. An aggravation claim focuses on your baseline before the crash compared to your function and pain after it. A new injury claim focuses on showing the new problem wasn't there before and lines up with the mechanics of the crash.

This is why your medical records from before the crash matter just as much as the records from after. If you were seeing a doctor for occasional back stiffness and after the crash you're dealing with radiating nerve pain, numbness, or a need for injections or surgery, that contrast is the evidence. Without a documented baseline, it's harder to show what actually changed, which gives the insurer room to claim nothing changed at all.

How insurers use your medical history against you

Insurance adjusters routinely request years of past medical records, not just records tied to the crash. They're looking for any prior mention of the same body part, any gap where you weren't being treated, and any inconsistency between what you told a doctor last year and what you're saying now. The goal is to build a story where your current pain is just the natural continuation of an old problem, not something the crash caused or worsened.

This tactic works best when there's no clear before-and-after picture. If you tell the adjuster you'd 'never had any problems' and the records show otherwise, that gap in your story gets used to question your credibility on everything else, not just the preexisting issue. Being upfront and specific about your prior health, rather than downplaying it, actually protects your claim instead of hurting it.

Why your own doctor's opinion on causation matters so much

A claim built on aggravation almost always needs a treating doctor, or sometimes a specialist, to state in the medical record that the crash worsened your condition or caused a new injury layered on top of an old one. Adjusters and defense lawyers look for this kind of statement specifically. If it's missing, they'll argue that the medical evidence doesn't actually connect the crash to your current symptoms.

This is one more reason continuity of treatment matters. If you stop treatment for weeks or months after the crash, or you see a different provider than the one who treated your prior condition, it becomes harder for any single doctor to speak clearly to what changed and when. Consistent treatment with providers who know your history gives you a cleaner record to work from.

What this looks like for common preexisting conditions

Degenerative disc disease is one of the most common fights. Insurers love to call disc problems 'age-related' and unrelated to a crash. But if you had no symptoms, or only mild ones, before a crash and now have significant pain, limited movement, or a need for treatment you never needed before, that change is the heart of the claim, not the degeneration itself.

The same pattern shows up with prior joint injuries, old fractures that healed, and even mental health conditions like anxiety or depression that a crash can intensify. In every version, the legal and medical focus is the same: not whether the condition existed, but whether the crash changed your symptoms, function, or need for care.

This article is general information for the public, not legal advice, and reading it does not create an attorney-client relationship. Nothing here predicts an outcome or the value of any claim. Laws and filing deadlines differ by state and change over time — talk with a lawyer about your own situation. Attorney advertising.