How Preexisting Conditions Can Affect an Injury Claim

A man I know had dealt with lower back pain for years. Degenerative disc disease, diagnosed in his mid-forties, managed with periodic physical therapy and occasional cortisone injections. He functioned fine. He worked. He lived his life.

Then a driver ran a stop sign and hit him from behind on a highway outside Muskegon.

The accident aggravated his spine in ways that went well beyond anything he’d dealt with before. He needed surgery. He missed four months of work. His recovery took over a year.

The first thing the other driver’s insurance company did after getting his medical authorization was pull every record they could find from the previous ten years. They found the degenerative disc disease diagnosis, the physical therapy, the injections. Their position was straightforward: his back problems predated the accident, his current symptoms were a continuation of the preexisting condition, and the accident wasn’t responsible for what he was experiencing.

That argument is made in nearly every personal injury case involving a spine injury. It works when the plaintiff’s documentation doesn’t clearly establish what changed after the accident. It worked less well in his case because his attorney built a medical record that specifically addressed it.

What Insurers Do With Preexisting Conditions

A preexisting condition is the most consistently used tool in an insurer’s effort to reduce or eliminate a personal injury claim. The logic is simple and it resonates with juries: if you were already hurt before the accident, how do we know the accident caused what you’re claiming now?

The answer matters legally and practically. Michigan follows a modified comparative fault rule, and in cases where a preexisting condition exists, the insurer argues that some or all of the current condition predates their insured’s negligence. Every percentage of the injury they can attribute to the preexisting condition rather than the accident reduces their obligation to pay for it.

This argument gets made on the basis of your own medical records. The records you provide access to when you sign a medical authorization for the insurance company. Records that show prior treatment, prior complaints, prior diagnoses. Records they use to build a narrative that what you’re experiencing now is old, not new.

The Eggshell Plaintiff Doctrine

What most injured people don’t know, and what insurers don’t volunteer, is that the law doesn’t require you to have been in perfect health before the accident to recover for what the accident did to you.

The eggshell plaintiff doctrine, recognized in Michigan and most states, holds that a defendant takes their victim as they find them. If you had a vulnerable back because of degenerative disc disease and the accident caused significantly more damage than it would have to a healthier spine, the defendant is responsible for the full extent of the harm, not just the portion a healthy person would have suffered.

Justia’s personal injury law resources cover this principle and the broader framework for personal injury claims, including how courts treat preexisting conditions in the damages analysis. Understanding that the law is on your side on this point doesn’t mean the insurer will concede it. It means you have a legal foundation to fight back from.

The eggshell doctrine doesn’t mean preexisting conditions are irrelevant. It means they don’t eliminate your claim. The argument becomes about what the accident specifically caused or aggravated, distinguished from what was already there, and that distinction is built through medical evidence.

The Aggravation Distinction

Aggravation of a preexisting condition is compensable. The accident doesn’t have to have created a problem from scratch. If a condition was stable, managed, and not significantly limiting your daily function, and the accident destabilized it, worsened it, or transformed it from something manageable into something that required surgery, that change is compensable.

The man from Muskegon had lived with degenerative disc disease for years without needing surgery. The accident changed that. His treating physician specifically documented that the force of the collision caused a herniation at a disc level where his prior imaging showed degeneration but not herniation, and that the herniation was what required surgical intervention.

That documentation is the foundation of the aggravation argument. Without it, the insurer’s narrative, that this was just his preexisting condition running its course, has nothing specific to push against.

With it, the argument becomes that his spine was vulnerable before the accident and that the accident caused specific, identifiable harm beyond what the preexisting condition had produced. The defendant is responsible for that harm. Not for the years of degenerative disease that predated the crash, but for what the crash specifically did to a spine that was already compromised.

Building the Medical Record to Support Aggravation

The medical record that exists before your attorney gets involved will be used by the insurer to support their narrative. The medical record built after the accident, if it’s built correctly, can counter that narrative with specific clinical findings.

Your treating physician needs to document the comparison explicitly. Not just your current diagnosis, but how it compares to your baseline before the accident. A physician who has access to your pre-accident imaging and can document specifically what changed, what was new, what got worse, and what the mechanism of the accident would explain, is providing the clinical foundation for a legally viable aggravation claim.

A baseline physical before the accident is obviously ideal. Most people don’t have one. What you can build is a comparison through your prior medical records showing the state of the condition before the accident versus the state documented after it. A spine that showed degenerative changes on a 2019 MRI but no herniation, compared to a post-accident MRI showing herniation at the same level, tells a story that has a foundation in objective imaging rather than just your account of how you felt.

Independent medical examinations are one of the tools insurers use to challenge this comparison. The physician they select examines you and typically finds that your current condition is attributable to the preexisting condition rather than the accident. Responding to an IME with your own treating physician’s specific findings and expert testimony from a physician familiar with the biomechanics of the accident type gives the factfinder competing expert opinions to evaluate rather than just the insurer’s expert speaking unopposed.

Prior Medical Records and What You Should Know

When you sign a medical authorization for the insurance company, they use it to pull your complete medical history, sometimes going back a decade or more. They’re looking for anything that documents the preexisting condition, any prior complaints that resemble current symptoms, and any gaps in treatment that they can use to argue your current symptoms predate the accident and aren’t related to it.

You can’t hide a preexisting condition and shouldn’t try. The insurer will find it. What you can do is make sure the record that exists after the accident clearly establishes the comparison point: what existed before, what changed after, and why the accident explains the change.

Your attorney should review your prior medical records before the insurer gets them, not to remove anything but to understand what the insurer is going to see and to build the counter-narrative before it’s needed. Going into the insurer’s record review without knowing what’s there is going into a negotiation without knowing your own position.

Social Media During a Preexisting Condition Claim

Insurance defense teams monitor social media during active claims. In a preexisting condition case this is particularly consequential.

A photograph from before the accident showing you doing something physical, skiing, hiking, lifting your grandchildren, works both ways. It establishes your functional baseline before the accident, which can support the aggravation argument. Defense teams use the same photographs to argue that your condition wasn’t limiting before the accident and that your current limitations are therefore exaggerated.

During an active claim, stay off social media about your condition, your activities, your treatment, and your daily function. The context that would make a photograph from a good day accurately represent your overall condition doesn’t travel with the photograph when it ends up in a demand response letter.

If you’re dealing with a preexisting condition defense in Michigan, the documentation and medical expert work that addresses it effectively takes time to build and requires starting early.

Shibley Law personal injury attorneys handle personal injury claims in Michigan and understand specifically how to build the medical causation arguments that distinguish accident-related aggravation from preexisting condition progression, and how to counter the independent medical examination findings that insurers use in these cases. Check their FindLaw attorney profile for background on the firm before reaching out.

The man from Muskegon recovered a fair settlement. His prior degenerative disc disease came up in every negotiation. His attorney had anticipated it from the beginning and had built the medical record around specifically addressing it.

The insurer’s argument wasn’t wrong that his spine had preexisting vulnerabilities. The argument they couldn’t sustain was that the accident was irrelevant to the specific harm that required surgery. That distinction, documented in his treating physician’s comparison of pre-accident and post-accident imaging, was what the case turned on.

Preexisting conditions complicate injury claims. They don’t eliminate them. The difference between a claim that gets reduced or denied because of a preexisting condition and one that recovers what it should comes down to whether anyone built the medical record that addresses the distinction from the beginning.

Author: Leland Bengtson

As a journalist, Leland Bengtson dedicated most of his career to law reporting. His greatest satisfaction is to convey legal matters to the public in a language that they can understand. He is active on various platforms and media outlets, writing about common legal issues that people confront every day. While medical malpractice is his strong suit, Leland covers plenty of other topics, including personal injury cases, family law, and other civil and even criminal legal matters.