Document name
Pre-Existing Conditions – Aggravation or Acceleration
Document number
POL 12/2017

Effective date: October 1, 2017

Application: All injuries on and after the effective date where there is a pre-existing condition.

Policy subject: Decision making - Principles


To establish adjudication guidelines for claims where pre-existing conditions exist.


Policy section content
Section detail

Pre-existing condition means a non-work related medical, physical or psychological condition that existed prior to the work-related injury. The existence of the condition must be medically confirmed, either pre-injury or post-injury, and may have been evident prior to the occurrence of the work injury or it may become evident afterwards.

Aggravation means, as the result of a work-related injury, a pre-existing condition is temporarily worsened.

Acceleration means, as the result of a work-related injury, a pre-existing condition is permanently worsened.


Policy section content
Section detail
  1. Section 2(1)(r) of The Workers’ Compensation Act, 2013 (the “Act”) specifies that an “injury” means all or any of the following arising out of and in the course of employment:
    1. The results of a willful and intentional act, not being the act of the worker;
    2. The results of a chance event occasioned by a physical or natural cause;
    3. A disabling or potentially disabling condition caused by an occupational disease;
    4. Any disablement.
  2. The Workers’ Compensation Board (WCB) has exclusive jurisdiction to determine all matters arising pursuant to the Act, specifically (Section 20):
    1. Whether any condition or death was caused by an injury,
    2. Whether an injury has arisen out of and in the course of employment, and
    3. The existence, degree and permanence of any functional impairment resulting from an injury.
  3. The WCB will not reject the claim of a worker or a dependant for compensation or reduce the amount of compensation payable by reason of a pre-existing condition of the worker, if the injury materially aggravates or accelerates the pre-existing condition to produce a loss of earnings or death (Section 49).


Policy section content
Section detail
  1. The decision to accept a claim is based on if the injury arose out of and in the course of employment (POL 07/2021, Arising Out of and In the Course of Employment). A worker’s pre-existing condition is not considered in the initial determination to accept a claim.
  2. While the WCB does not assume any responsibility for a worker’s pre-existing condition, the WCB will determine if a work-related injury resulted in either an aggravation or acceleration of a worker’s pre-existing condition.
  3. The WCB will review all available information about a worker’s pre-existing condition to determine the extent of benefits (e.g., wage loss, medical, etc.) a worker is eligible to receive.


  1. If the work-related injury results in an aggravation of the pre-existing condition, the WCB is responsible for benefits until the worker has recovered from the effects of the work-related injury.


  1. If the work-related injury results in an acceleration of the pre-existing condition, the WCB is responsible for any benefits related to the combined effects of the injury and any ongoing impacts the work-related injury has on the pre-existing condition.
  2. To confirm that an acceleration of a pre-existing condition has occurred, medical confirmation is required through diagnostic testing (e.g., x-ray, computerized tomography (CT) scan, magnetic resonance imaging (MRI) scan, mental health assessment).

Cost Relief

  1. An employer may be eligible for cost relief for claims involving a pre-existing condition under POL 03/2021, Second Injury and Re-employment Reserve.

Policy references

Policy reference content

Section heading

Legislative Authority

Section detail

The Workers’ Compensation Act, 2013
Sections 2(1)(r), 20, 26, 31, 49, 103

Section heading

Document History

Section detail

(1)    POL and PRO 01/2000, Pre-Existing Condition – Section 49 (effective May 1, 2000 to September 30, 2017).
(2)    POL 17/94, Pre-Existing Conditions (effective August 16, 1994 to April 30, 2000).

Section heading


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