Workers compensation is premised on the concept that workers should be compensated for injuries or disablements sustained in the course of their employment. Causation is the key factor in determining whether a worker’s injuries are compensable. In determining questions of causation, issues often arise as to whether the injury was truly sustained in the course of employment or was the result of some pre-existing condition suffered by the worker. In such situations, a worker’s entitlement to compensation can be complex.
This article considers the role of pre-existing conditions on the issue of entitlement in workers compensation law in Ontario, Canada. It focuses on the use of the “thin skull” rule by Ontario’s Workplace Safety and Insurance Appeals Tribunal (“Tribunal”) and Workplace Safety and Insurance Board (“Board”). Finally, this article identifies relief available for employers who face situations where the severity of their worker’s injury is enhanced by the existence of a pre-existing injury.
In Ontario, a “significant contributing factor” analysis is used to determine whether a worker’s injury or condition is compensable. This test focuses on whether the work itself made a significant contribution to the worker’s injury. The work need not be the sole contributing factor to the injury. As long as the work makes more than a de minimus contribution to the injury, the worker will be entitled to workers compensation.
Canadian common law has recognized a limit to the thin skull principle in situations where a pre-existing condition is so large a causal factor in an injury that it overwhelms the significance of the conduct of the tortfeasor. This concept is known as the “crumbling skull” rule.
The Board operates a Second Injury and Enhancement Fund (SIEF) to provide employers with financial relief where a pre-existing condition enhances or prolongs a work-related disability. By providing employers with such financial relief, the SIEF encourages employers to hire workers with disabilities.
Contributing Author: Joseph Cohen-Lyons is an associate lawyer at the Hicks Morley Toronto, Canada office and currently practices in all areas of labour and employment law providing advice and representation to employers and management. Contact him at: firstname.lastname@example.org or 416-864-7213.
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Do not use this information without independent verification. All state laws vary. You should consult with your insurance broker or agent about workers comp issues.