How Pre-Existing Conditions Are Treated in Ontario Personal Injury Claims

July 22, 2025, Kitchener, Ontario

Posted by: Robert Deutschmann, Personal Injury Lawyer

Many injured Ontarians worry that their pre-existing health conditions could hurt their chances of compensation after an accident. Understanding how Ontario law views these cases can give you peace of mind and strategic advantage.

At Deutschmann de Koning Personal Injury Law, we help clients demonstrate the impact of new injuries despite past conditions.

The “Eggshell Plaintiff” Principle

Ontario courts apply the “eggshell plaintiff” rule: a defendant must take the plaintiff as they find them. This means:

• If an accident aggravates a pre-existing condition, the defendant is responsible for the full extent of the harm caused
• Even if the injury was more severe because of prior issues, the plaintiff can claim damages for the worsened condition

Gathering Evidence Is Key

Proving how a pre-existing condition was aggravated requires:

• Medical records before and after the accident
• Expert medical testimony linking the new injury to the worsening condition
• Documentation of increased pain, disability, or treatment needs

How Our Lawyers Will Help You

At Deutschmann de Koning Law, we carefully build cases to show the connection between the accident and your current condition. This helps maximize compensation and protects you from insurance company attempts to deny responsibility.

Injured and worried about pre-existing conditions? Get expert legal advice from Deutschmann de Koning Personal Injury Law. Visit ddinjurylaw.com for a free consultation today.

About Deutschmann de Koning Law

Deutschmann de Koning Law serves South-Western Ontario with offices in Kitchener-Waterloo, Cambridge, Woodstock, Brantford, Stratford and Ayr. The law practice of Robert Deutschmann and Nick de Koning focuses almost exclusively in personal injury and disability insurance matters. For more information, please visit www.ddinjurylaw.com or call us at 1-519-742-7774.