A defendant can be responsible for the aggravation of a pre-existing condition when the crash made that condition worse. Washington applies what is commonly called the eggshell plaintiff rule alongside the aggravation doctrine: a defendant takes the plaintiff as they find them. If the crash aggravated, accelerated, or reactivated a condition, the defendant can be liable for that aggravation — even if the underlying condition made you more vulnerable to injury in the first place.
Vulnerability, by itself, is not a defense.
Washington's Aggravation and Eggshell Plaintiff Rules
A defendant takes an injured person as found and can be responsible for harm caused by aggravating a pre-existing condition.
How Insurers Use Prior Medical History
Expect prior medical history to be used as a shield. A knee surgery from years ago becomes "proof" that the post-crash knee pain was already there. An old back complaint becomes the explanation for current lumbar symptoms. The defense-hired independent medical examiner in these cases is retained, in practice, to find pre-existing conditions to blame.
None of that means the argument is correct. It means the argument is coming, and the answer has to be built in advance.
Establishing the Pre-Collision Medical Baseline
What separates an old injury from a new one is documentation of the before versus the after. Pre-crash medical records establish what was present, what was symptomatic, what was being treated, and what had resolved.
If you had shoulder surgery three years ago, recovered fully, and were asymptomatic when a car hit you and injured the same shoulder, the prior surgery is context — not a defense. The records showing a healed, functional shoulder before the crash are what carry that argument.
Medical Evidence Linking the Crash to Aggravation
Medical records and opinion evidence can separate the pre-collision baseline from new symptoms, treatment, and limitations caused by the crash.
When Unrelated or Degenerative Conditions Complicate a Claim
The harder cases are the ones where the prior condition was actively symptomatic, untreated, and functionally limiting in the same way as the post-crash complaint. Disentangling the crash's contribution from the underlying condition in those situations requires careful medical analysis and, frequently, expert testimony. The outcome depends heavily on the specific medical facts.
These claims are not lost causes. They demand more thorough documentation and more careful expert work than clean-slate injuries — which is a reason to involve counsel early, not a reason to assume the claim is not worth pursuing.
General legal information only. Specific facts, policy language, parties, and deadlines can change the analysis.