Aggravation Basis


In cases where the worker has a pre-accident impairment and suffers a minor work-related injury/disease to the same body part or system, the WSIB considers entitlement to benefits on an aggravation basis.

Generally, entitlement is considered for the acute episode only and benefits continue until the worker returns to the pre-accident state.


The purpose of this policy is to outline what a pre-accident impairment is and provide direction for the adjudication of claims where a minor work-related accident aggravates the worker’s pre-accident impairment.


Decision-makers should first determine entitlement in the claim, see 11-01-01, Adjudicative Process and 15-02-01, Definition of an Accident.

This policy applies where a minor work-related accident aggravates a pre-accident impairment. The intent is to limit entitlement to the injury/disease that is work-related. If a claim is allowed on an aggravation basis, benefits are paid for the acute episode only (temporary period of time) and entitlement ends when the worker returns to the pre-accident state.

This policy does not apply where there is no pre-accident impairment (see Definitions), or the severity of the accident/exposure on its own would have resulted in additional impairment.

Where a pre-existing condition has not produced periods of impairment/disease requiring health care and has not caused a disruption in employment, but is now impacting the ongoing impairment of the work-related injury/disease, see 15-02-03, Pre-existing Conditions.


Aggravation: is the temporary effect that a minor work-related injury/disease has on a pre-accident impairment requiring health care and/or leading to a loss of earnings.

Minor accident: is one that, in the absence of a pre-accident impairment, would be expected to cause a non-disabling or minor disabling injury/disease.

Pre-accident impairment: is a condition that has produced periods of impairment/disease requiring health care and has caused a disruption in employment (lost time and/or modified work). Although the period of time cannot be defined, the decision-maker may use a one to two year timeframe as a guide.

Pre-accident state: is the worker's level of impairment and work capacity prior to the work-related injury/disease.

Determining entitlement for aggravation of a pre-accident impairment

Entitlement for aggravation of a pre-accident impairment is accepted when the clinical evidence demonstrates a relationship between the pre-accident impairment and the degree of impairment resulting from the accident, and the impairment after the accident is greater than would be expected owing to the pre-accident impairment.

When it is accepted that a minor work-related accident aggravated a pre-accident impairment benefits are paid until the worker returns to the pre-accident state.

Determining pre-accident impairment

Before entitlement for an aggravation is considered, the decision-maker must determine if a pre-accident impairment exists. Evidence of this includes, but is not limited to, the worker having

  • a previously identified and symptomatic medical condition/impairment
  • medical precautions/restrictions and performing modified work prior to the accident
  • received regular health care treatments prior to the accident
  • lost time from work prior to the accident.

This information can be obtained by reviewing information such as

  • prior health care documentation (e.g., x-rays, hospital records, operative reports)
  • prior claim(s)
  • statements from the worker, the employer, or co-workers
  • employment records
  • work history.

In most cases, evidence of a pre-accident impairment is available at the initial entitlement stage of the claim. However, if at any point evidence of a pre-accident impairment is shown to exist, the question of allowance on an aggravation basis may be considered.

New accident vs recurrence

If a pre-accident impairment is due to a work-related injury/disease, further entitlement may be considered as a recurrence. This would occur where it is difficult to identify a specific incident or action that has increased the worker's impairment, see 15-02-05, Recurrences.

Ongoing entitlement

Decision-makers are responsible for limiting entitlement in claims allowed on an aggravation basis. The worker’s clinical status is monitored to determine if the worker has reached the pre-accident state. If a worker remains off work after reaching the pre-accident state, the decision-maker discontinues benefits and advises the workplace parties.

Because entitlement is limited to the acute episode only and ends when the worker returns to the pre-accident state, the WSIB generally does not consider recurrence entitlement or permanent impairment entitlement in cases where the claim was allowed on an aggravation basis.

Permanent impairment

In some cases, workers never return to the pre-accident state. If there is a permanent worsening of the pre-accident impairment, the decision-maker may determine that the work-related injury/disease has permanently aggravated the pre-accident impairment. If clinical evidence confirms that the work-related injury/disease permanently increased the worker’s pre-accident impairment, the worker may be entitled to a non-economic loss benefit. For more information, see 18-05-03, Determining the Degree of Permanent Impairment.

For information about a permanent aggravation of a pre-existing conditions, see 15-02-03, Pre-existing Conditions and 11-01-05, Determining Permanent Impairment.

Special cases

For some exceptional conditions, there may be some limitations in entitlement. See
15-03-10, Heart Conditions
15-04-08, Hernia
15-04-02, Psychotraumatic Disability
15-04-12, Fume Toxicity – TDI
16-02-03, Skin Diseases

Application date

This policy applies to all decisions made on or after November 1, 2014, for all accidents.

Policy review schedule

This policy will be reviewed within five years of the application date.

Document History

This document replaces 11-01-15 dated July 18, 2008.


Legislative Authority

Workplace Safety and Insurance Act, 1997, as amended 
Sections 2(1), 13(1), 43(1), 46(1), 118

Workers’ Compensation Act, R.S.O. 1990, as amended
Sections 1(1), 4(1), 36, 42, 69


#1, September 22, 2014, Page 518