Pre-Existing Conditions and Car Accidents — The Eggshell Skull Rule in Arizona

“But you already had back problems.” It’s the insurance company’s favorite defense. If you had any pre-existing medical condition — a prior back injury, arthritis, a previous surgery — they’ll try to blame your symptoms on the pre-existing condition instead of the accident.

The Eggshell Skull Rule

Arizona follows the eggshell skull doctrine (also called the “thin skull” rule). It says: a defendant takes the plaintiff as they find them. If you have a pre-existing condition that makes you more vulnerable to injury, the defendant is still liable for the full extent of your injuries — even if a healthier person would have been less hurt.

If you had a degenerative disc that was manageable before the accident and the crash turned it into a condition requiring surgery, the at-fault driver is responsible for the surgery — not just the “incremental” worsening.

Aggravation vs. Causation

The key legal concept is aggravation. You don’t have to prove the accident caused a brand-new injury. You have to prove it aggravated — made worse — your pre-existing condition. The damages are measured by the difference between your condition before the accident and after.

How to Protect Your Claim

Be honest about your pre-existing conditions. Don’t hide them — the insurance company will find your prior medical records. Concealing a pre-existing condition destroys your credibility. Instead, your attorney presents the medical evidence showing what changed after the accident.

Your treating doctor’s testimony is critical. They need to clearly state that the accident aggravated your condition, worsened your symptoms, or accelerated degeneration that would not have occurred (or would have occurred much later) without the crash.

The Law Badgers handle pre-existing condition cases regularly. The eggshell skull rule is firmly established in Arizona law — and we know how to use it. Call (833) DTF-IGHT.