Unlike all other Canadian jurisdictions, Ontario's workers compensation regime was without a specific policy on pre-existing conditions, until now. On November 1, 2014, a new Workplace Safety and Insurance Board ("WSIB") policy, Pre-Existing Conditions, came into force. The underlying goal of the policy is to provide decision makers with guidance on how to draw the work-related/non-work-related line when it comes to adjudicating compensation claims involving pre-existing conditions.

The Pre-Existing Conditions policy is available on the WSIB website as Operational Policy Manual 15-02-03.

Challenges of Adjudicating Claims with Pre-Existing Conditions

Workers compensation regimes in Canada are based on the premise that workers are entitled to benefits when they sustain a work-related injury. In many cases, the link between an injury and a work-related event is clear. When pre-existing conditions are present, however, the adjudication process can become more challenging. Pre-existing conditions are typically viewed as conditions that do not have their origins in the workplace but instead are the result of non-work-related factors such as degeneration or previous injuries. When workplace and non-workplace factors are both present, questions arise as to how to adjudicate such claims in a way that is fair to the worker, while also ensuring that the worker's compensation system is not compensating for injuries that are the result of non-workplace conditions.

Ontario's New Policy: Core Elements

Ontario's new policy purports to provide guidance to decision makers in order to increase consistency in outcomes for both workers and employers. The core elements of the policy include the following:

  1. Definition of Pre-Existing Condition: A pre-existing condition is defined in the policy as, "any condition that existed prior to a work-related injury/disease, and may include injuries, diseases, degenerative conditions, and psychiatric conditions." The existence of the condition must be confirmed by pre-injury or post-injury clinical evidence.
  2. Entitlement: The policy explicitly states that initial entitlement will not be denied due to the existence of a pre-existing condition. Further, ongoing entitlement may only be affected where it is shown that the pre-existing condition is impacting the worker's ongoing impairment.
  3. "Crumbling Skull" and "Thin Skull" Legal Principles: The policy encompasses the "crumbling skull" and "thin skull" doctrines, which are well established legal principles and components of decision making at the WSIB. The "crumbling skull" doctrine seeks to limit entitlement to benefits to only the injury that is work-related. This means that workers are entitled to benefits only for the acute episode.  Benefits will stop as soon as the worker returns to his or her pre-accident state. The "thin skull" doctrine holds that the compensation system must take the worker as it finds him or her: pre-existing, pre-dispositions do not affect entitlement.
  4. Work-Relatedness and the "Significant Contributing Factor" Test: The "significant contributing factor" test is well established in WSIB practice and court jurisprudence. The new Policy includes the "significant contributing factor" test and states that when assessing the impact of the pre-existing condition on the worker's ongoing impairment, the decision maker must determine whether the work-related injury continues to be a significant contributing factor.

Considerations for Employers

The question of how to fairly assess cases involving a worker who has a pre-existing condition remains complex. Although Ontario's new policy aims to provide clarity and consistency to claim-related outcomes, employers should always keep a close eye on claims involving pre-existing conditions and take steps to ensure that decision makers are following the requirements set out in the law and Policy with respect to pre-existing conditions - particularly the following:

  • Objective medical evidence is crucial in any case involving pre-existing conditions;
  • Although employers are responsible for injuries that are at least a significant contributing factor, they are not responsible for compensating workers for injuries that are unduly remote (e.g. a non-work-related contributing factor so dominant as to constitute an "intervening cause" which breaks the chain of causation); and
  • The presence of a pre-existing condition does not necessarily mean it has any impact on a worker's impairment. Ontario's new policy, for example, sets out a number of factors for the decision maker to consider when determining initial and ongoing entitlement, including whether the impairment affects the same body part as the pre-existing condition and whether the impairment continues beyond the expected recovery period, given the work- related injury.

Financial relief may be available in cases involving pre-existing conditions through the WSIB's Secondary Injury Enhancement Fund or aggravation basis policy. Finally, employers should always exercise their right to appeal any and all questionable claims and decisions.