Written by Short answer: Illinois follows the “eggshell plaintiff” doctrine, which means the at-fault party takes the injured person as they find them. If a crash, fall, or other negligent act aggravates a pre-existing condition (a prior back injury, arthritis, an old TBI, a vulnerable spine), the at-fault party is responsible for the aggravation, even though the same impact would not have hurt a healthier person as severely. The doctrine is one of the most important protections for Illinois injury victims, and the recurring carrier defense (“your symptoms are from your pre-existing condition, not from our insured”) is defeated by it when the medicine is developed properly.
In my experience representing Illinois injury victims, the pre-existing condition defense is the carrier’s single most common argument in soft-tissue, orthopedic, and chronic-pain cases. Insurance adjusters reflexively attribute current symptoms to age, prior injury, degenerative findings, or any documented history of the same body part. The eggshell plaintiff doctrine is the legal answer; this guide explains how it works and how to use it.
What the Eggshell Plaintiff Doctrine Says
Illinois follows the common-law rule that a tortfeasor takes the victim as they find them. If an at-fault driver’s negligence aggravates an underlying condition, the at-fault driver is liable for the aggravation. The pre-existing condition is not a defense to liability; it shapes the damages analysis.
| Scenario | What the eggshell rule allows recovery for |
|---|---|
| Pre-existing herniated disc, asymptomatic before crash, symptomatic after | The full extent of post-crash symptoms and treatment |
| Prior knee surgery, healed, then crash injures the same knee | The new injury and any treatment of the aggravation |
| Arthritis or degenerative changes on imaging, no symptoms before, symptoms after | The post-crash symptomatic phase, even if the imaging looks “old” |
| Prior TBI, recovered, then concussion in crash | The new concussion and any worsening of cognitive baseline |
| Mental health condition aggravated by trauma of the crash | The post-crash psychological impact |
The Aggravation Burden
The plaintiff has the burden to prove that the crash aggravated the pre-existing condition, separating the new harm from the baseline. This requires:
- Pre-crash medical records showing the baseline (which symptoms existed, which did not)
- Post-crash medical records showing the change (new symptoms, increased severity, new findings on imaging)
- A treating physician’s opinion linking the change to the crash
- Sometimes expert testimony from an orthopedic surgeon, neurologist, or pain management specialist
If the plaintiff cannot separate the new harm from the baseline, the case can lose value or fail entirely. The legal protection is robust; the medical proof has to be developed deliberately.
How Carriers Attack the Eggshell Plaintiff
Insurance adjusters and defense counsel use a consistent set of arguments:
- “Symptoms are from age, not the crash.” Degenerative findings on MRI become evidence that current pain is age-related.
- “You had this same complaint before.” Any prior chiropractor visit, urgent care record, or doctor note mentioning the body part becomes the cause attribution.
- “Imaging shows old changes.” Imaging of degenerative disease is presented as proof the injury was not crash-related.
- “Independent medical exam confirms pre-existing.” The carrier’s IME doctor concludes current symptoms are unrelated.
- “Treatment is for the chronic condition.” Ongoing care is attributed to the baseline, not the aggravation.
Practical Steps for Eggshell Plaintiffs
- Disclose pre-existing conditions truthfully. Hiding them creates credibility problems when records emerge. Tell your lawyer everything; let them frame it correctly.
- Gather pre-crash records. The contrast between pre-crash baseline and post-crash symptoms is the proof. Pull the records affirmatively rather than waiting for the defense to.
- Use specific symptom descriptions. “I had occasional stiffness once a month before; now I have constant pain that wakes me up at night” is more useful than “I had some pain before but more now.”
- Document the activities you can no longer do. Loss-of-normal-life damages are highly visible in eggshell cases.
- Get a treating physician on the record. A clear written opinion on aggravation at the right point in treatment is worth far more than the same opinion offered for the first time at deposition.
Frequently Asked Questions
If I had a prior back injury, can I still recover for a new back injury from a crash?
Yes, under the eggshell plaintiff rule. The recovery is for the aggravation – the worsening caused by the crash. The medical proof has to separate the baseline from the new harm.
Does the eggshell rule apply if my pre-existing condition was asymptomatic?
Yes, and these are often the strongest cases. If imaging shows pre-existing degenerative changes but you had no symptoms before the crash, and you have symptoms after, the case is straightforward.
What if I’m not sure when my symptoms started?
Get medical records covering the year or two before the crash. The records will show what you were complaining of and when. Most clients are surprised to find their pre-crash baseline was lower than they remembered.
Can the carrier subpoena my entire medical history?
In litigation, yes, but the scope is limited by relevance. Records for unrelated body parts and unrelated time periods are typically protected. Your lawyer objects to overbroad requests.
What about psychological pre-existing conditions?
The eggshell rule applies to psychological harm as well. A prior anxiety or depression diagnosis does not bar recovery for crash-related PTSD or worsened mental-health symptoms; it shapes the damages analysis.
Authoritative Sources
- Illinois Pattern Jury Instructions (IPI) on aggravation of pre-existing condition
- 735 ILCS 5/2-1116 – Modified comparative fault
- Illinois Courts
