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Note: This is not a policy; it is a supplementary document to illustrate how the WSIB will administer the Workplace Safety and Insurance Act, 1997, (WSIA) and Policy 15-02-03 Pre-existing Conditions in practice. If there is a conflict between this Administrative Practice Document and the WSIA and/or WSIB policy, the decision-maker will rely on the WSIA and/or WSIB policy.
Key principles
- The WSIA directs that compensation be provided for work-related injuries and occupational diseases.
- We will not deny entitlement for a work-related injury or illness because a worker has a pre-existing condition.
- Decision-makers establish the work-relatedness of an injury or illness when determining initial entitlement. Decision-makers continue to evaluate the work-relatedness of a worker’s ongoing impairment throughout the life of a claim.
- When a work-related injury or illness and a pre-existing condition are factors in a worker’s ongoing impairment, we determine ongoing entitlement based on the causation standard of “significant contributing factor”.
- The “thin skull” and “crumbling skull” doctrines are well-established legal principles that are components of decision-making at the WSIB.
- Based on the “thin skull” principle, we take the worker as we find them. Entitlement is not denied because a worker has a pre-existing condition that makes them more susceptible to injury. We compensate the worker for the full effect of the work-related injury even if the injury is more severe than expected or takes longer to recover due to the pre-existing condition.
- Based on the “crumbling skull” principle, we recognize that while a work-related injury exists, the pre-existing condition and its effects were inherent in the worker at the time the work-related injury occurred. The WSIB compensates the worker for the effects of the work-related injury but not the effects of the pre-existing condition, which the worker would have experienced anyway.
- We make decisions based on the merits and justice of each case.
- When the evidence for and against an issue relating to a claim are evenly balanced, the benefit of doubt is given to the worker who experienced a workplace injury or illness.
Definitions
Impairment
Impairment is a physical or functional abnormality or loss (including disfigurement), which results from an injury or illness and any psychological damage arising from the abnormality or loss.
Pre-existing condition
A pre-existing condition is any condition that existed prior to a work-related injury or illness and may include injuries, illnesses, degenerative conditions and psychological conditions. The existence of the condition must be confirmed by pre-injury or post-injury clinical evidence. The pre-existing condition may have been evident before the work-related injury or illness occurred, or it may become evident afterwards.
Pre-existing conditions include but are not limited to:
- conditions that have produced periods of impairment or illness requiring health care and have caused a disruption in employment prior to the workplace injury or illness, as defined in 15-02-04, Aggravation Basis,
- underlying or asymptomatic conditions which only manifest themselves post-injury or illness as defined in 14-05-03, Second Injury and Enhancement Fund (SIEF), and
- work-related permanent impairments for which the WSIB has granted a permanent disability or non-economic loss benefit prior to the most recent workplace incident.
Introduction
Section 13 of the Workplace Safety and Insurance Act, 1997 (WSIA), directs that workers who are injured by accident arising out of and in the course of their employment or who acquire an occupational disease that occurs due to the nature of their employment are entitled to compensation. The Workplace Safety and Insurance Board (WSIB) provides benefits to workers with an impairment resulting from a work-related injury or illness.
The pre-requisite of work-relatedness outlined in section 13 of the WSIA applies at every stage in the life of a claim – initial entitlement, ongoing entitlement and determining permanent impairment. The impairment must be attributable, or causally linked, to the work-related injury or illness for entitlement to benefits to continue. Decision-makers continually assess and monitor the clinical evidence to confirm ongoing impairment resulting from the work-related injury or illness.
The policy on pre-existing conditions provides guidance on determining work-relatedness of the ongoing impairment where there is evidence of a pre-existing condition and both the work-related injury or illness and pre-existing condition are contributing to the ongoing impairment. The policy outlines “significant contributing factor” as the standard of causation for review in determining work-relatedness of the ongoing impairment. It also includes the criteria for determining when the contribution of the work-related injury or illness is no longer sufficiently significant to support continuing entitlement to benefits.
This document focuses on the application of the policy on pre-existing conditions. It includes references to the application of the policies on aggravation basis and permanent impairments, noting they also relate to the issue of work-relatedness of the impairment.
Initial entitlement
WSIB decision-makers determine entitlement according to the WSIA and policies 15-02-01, Definition of an Accident and 11-01-01, Adjudicative Process. They may also consider additional policies that are relevant and applicable to the facts of the case. All decisions are made on the merits and justice of the claim based on the case-specific facts, in accordance with policy and law. Where the evidence for and against the issue in a claim is approximately equal in weight, the worker who experienced a workplace injury or illness is given the benefit of doubt and the claim is allowed. (See Policy 11-01-03, Merits and Justice and Policy 11-01-13, Benefit of Doubt.)
When the decision-maker establishes the worker was injured by accident arising out of and in the course of the employment, or has an occupational disease that occurred due to the nature of the employment, the claim is allowed. This is the case even when there is evidence of a pre-existing condition, which may have increased the worker’s susceptibility to injury or illness. We provide compensation for the full effect of the work-related injury or illness, even when the effects are worse than expected, or when recovery takes longer due to a pre-existing condition.
The mere existence of a pre-existing condition is not grounds to disqualify a worker from entitlement to WSIB benefits. Policy 15-02-03, Pre-existing Conditions reinforces this long-standing practice.
For the remainder of this document, the term ‘injury’ includes an occupational disease.
What is an impairment?
As noted above, impairment is defined as a physical or functional abnormality or loss (including disfigurement) which results from an injury or illness and any psychological damage arising from the abnormality or loss. For the definition, see Policy 11-01-05, Determining Permanent Impairment.
The existence of an impairment is established through the clinical findings found in the medical records. A clinical finding is a sign that can be seen, heard, felt, or measured by a health care professional. Clinical findings of impairment include, but are not limited to:
- measurable clinical findings of physical loss or abnormality (e.g., abnormal range of motion , evidence of complication in healing)
- measurable clinical findings of functional loss or abnormality (e.g., abnormal radiological findings, abnormal neurological findings)
In the absence of clinical findings of impairment, factors such as pain complaints and the duration or perceived severity of the treatment received are not considered to be indicators of impairment. For example, surgery is a therapeutic intervention designed to improve or fully restore function. Surgery, in and of itself, is not an indicator of impairment. The post-operative outcome and associated clinical findings may indicate ongoing impairment.
When a worker has a pre-existing condition, the clinical evidence of impairment following the work-related injury or illness may be due to the work-related injury or illness, the pre-existing condition, or a combination of the two. Where the pre-existing condition is non-work-related, we need to determine the work-relatedness of the ongoing impairment to ensure WSIB benefits are provided for work-related injuries as directed by the WSIA. Where the pre-existing condition is a work-related condition, decision-makers must determine if the ongoing impairment is due to the current injury or the previous injury.
Monitoring and assessing ongoing impairment
After initial entitlement for a work-related injury or illness is established, decision-makers continually monitor the worker’s recovery, take appropriate action to promote recovery and facilitate return to work, and continue benefits and services as applicable. When a pre-existing condition is evident, or becomes evident, decision-makers will consider Policy 15-02-03, Pre-existing Conditions, while monitoring the work-relatedness of the ongoing impairment and evaluating whether the pre-existing condition is impacting the worker’s ongoing impairment.
To determine if the pre-existing condition is impacting the worker’s ongoing impairment, decision-makers must obtain sufficient relevant information to understand the nature of the pre-existing condition. Decision-makers may:
- contact the worker to obtain information about when and how the condition started, details about symptoms and treatment received for the condition, and any work impacts
- contact the employer to confirm any complaints, lost time from work and/or work accommodations as a result of the pre-existing condition
- obtain relevant clinical records from the worker’s family physician and other health care providers to confirm the nature of the pre-existing condition and resulting impairment
The decision-maker requests the relevant clinical records relating to the pre-existing condition based on the information obtained from the worker, their employer and from the clinical records on file.
Once the decision-maker has gathered the information and received the relevant clinical records, they must consider the nature of the work-related injury or illness, the ongoing impairment and the pre-existing condition by considering the:
- mechanism of injury
- diagnosis and associated clinical findings of the work-related injury or illness
- diagnosis and associated clinical findings of the pre-existing condition
- impairment resulting from the pre-existing condition prior to the workplace incident
- worker’s pre-injury functional abilities and pre-injury job duties
A full understanding of both the work-related injury or illness and the pre-existing condition is necessary to determine the extent and severity of both the work-related injury or illness and the pre-existing condition. This enables decision-makers to evaluate and determine the impact, if any, of the pre-existing condition on the ongoing impairment and/or whether the work-related injury or illness has aggravated the pre-existing condition.
Once the decision-maker has established the existence of a pre-existing condition, they must continually assess and monitor the evidence in the claim to determine whether the pre-existing condition is, or becomes, a contributing factor in the worker’s ongoing impairment.
As stated in Policy 15-02-03, Pre-existing Conditions, the decision-maker determines whether the pre-existing condition is impacting the worker’s ongoing impairment by considering whether
- the impairment affects the same body part or system as the pre-existing condition
- the impairment continues beyond the expected recovery period, given the work-related injury or illness
- the impairment is unexpectedly severe given the work-related injury or illness
- there is a change in the worker’s ability to perform the pre-injury or illness work beyond what is expected, given the work-related injury or illness
Allowance on an aggravation basis
At any point where assessment of the clinical records indicates there was pre-injury or illness impairment due to a pre-existing condition, as defined in Policy 15-02-04, Aggravation Basis, the decision-maker will review the initial entitlement decision.
To consider initial entitlement under policy 15-02-04, Aggravation Basis, two criteria must be met. The worker must first have a pre-accident impairment and then suffer a minor work-related injury to the area of injury. Allowance on an aggravation basis accepts entitlement for the acute episode only, until the worker returns to the pre-injury or illness state. The pre-injury or illness state is the worker’s level of impairment and work capacity prior to the work-related injury or illness.
The decision-maker must consider whether a pre-existing condition has an impact on the worker’s ongoing work-related injury or illness.
Despite the existence of a pre-existing condition and any associated impairment, benefits will end when the
- work-related injury or illness recovers fully as expected,
- work-related injury or illness recovers fully, even if the recovery takes longer due to the pre-existing condition, or
- aggravation of the pre-existing condition resolves.
The decision-maker is required to monitor the clinical evidence to identify the point at which the work-related injury or illness ceases to be a significant contributing factor to the ongoing impairment, or the worker has reached their pre-accident state.
To determine this, the decision-maker considers whether the work-related injury or illness on its own would cause a similar level of impairment and whether the worker’s current level of impairment would continue even if the work-related injury or illness had not occurred.
Decision-makers will consider all the information and clinical evidence in the claim and consider factors, such as:
- symptomology and clinical findings that are attributable to the work-related injury or illness versus those attributable to the pre-existing condition
- compatibility of any new diagnoses or clinical findings to the mechanism of the accident and the accepted work-related injury or illness
- clinical evidence of improvement/resolution or progression/deterioration of the symptomology and clinical findings attributable to the work-related injury or illness
- clinical evidence of improvement/resolution or progression/deterioration of the symptomology and clinical findings attributable to the pre-existing condition
- whether the pre-injury job was a suitable occupation for the worker, given any functional limitations related to their pre-existing condition
- the weight of the clinical evidence when the health care professionals involved in the case have conflicting opinions on diagnosis, prognosis, treatment, causation and functional abilities or physical precautions
Decision-makers may also obtain a clinical opinion for assistance with issues of causation, mechanism of injury, pathology and interpretation of the clinical evidence on file.
In some cases, the above considerations may reveal the contribution of the pre-existing condition to the worker’s ongoing impairment is so significant, in comparison to the work-related injury or illness, that it renders the contribution of the work-related injury or illness insignificant. The pre-existing condition would then be considered to have overwhelmed the work-related injury or illness and entitlement to ongoing benefits and services ends.
Permanent impairments with pre-existing conditions
A worker is entitled to compensation for a permanent impairment resulting from a work-related injury or illness.
The worker’s permanent impairment is determined as outlined in Policy 18-05-03, Determining the Degree of Permanent Impairment. When a pre-existing condition is contributing to the degree of total impairment to the same area of the body as the work-related injury or illness, the non-economic loss decision-maker:
- rates the total impairment to the area according to the prescribed rating schedule
- determines the rating for the pre-existing condition according to the prescribed rating schedule, and
- subtracts the rating for the pre-existing condition from the total impairment rating to get the rating for the new work-related impairment.
Where the pre-existing condition is considered to have overwhelmed the impact of the work-related injury or illness to the ongoing impairment, it is generally unlikely that a work-related permanent impairment exists.
Conclusion
To comply with the pre-requisite of work-relatedness outlined in section 13 of the WSIA, the WSIB must consider the clinical evidence of a pre-existing condition that affects the same area of the body or system as the work-related injury or illness when determining ongoing entitlement in a claim. The mere existence of a pre-existing condition does not disqualify a worker from initial entitlement for a work-related injury or illness, nor does it automatically affect their ongoing entitlement.
The intent of Policy 15-02-03, Pre-existing Conditions, is to provide clarity and consistency in decision-making and outcomes for both workers with workplace injuries and illnesses and their employers by setting a fair threshold for when benefits may end. When both the work-related injury or illness and the pre-existing condition are contributing to the ongoing impairment, the WSIB will continue ongoing benefits until the contribution of the pre-existing condition to the worker’s ongoing impairment becomes so great that it overwhelms that of the work-related injury or illness.
Document history:
December 2014 – Initial release to supplement new WSIB policy on pre-existing conditions (15-02-03)
January 2023 – Reviewed
Scheduled review:
January 2028