Highlights of Noteworthy Decisions

Decision 259 22
P. Allen
  • Causation (thin skull doctrine)
  • Permanent impairment {NEL} (degree of impairment) (knee)
  • Preexisting condition (knee condition)
  • Preexisting condition (osteoarthritis)
  • Permanent impairment {NEL} (rating schedule) (AMA Guides)
  • Apportionment (non-economic loss) (preexisting conditions)

The worker appealed an ARO decision which determined that her Non-Economic Loss (NEL) award of 2% for her left knee was appropriately determined by the NEL Clinical Specialist. The Vice-Chair determined that the worker's asymptomatic pre-existing conditions of osteoarthritis and meniscus tear in her left knee had been properly deducted from the worker's NEL award.

The Vice-Chair pointed to Document No. 18-05-03, which describes the three-step process for factoring out "pre-existing conditions and prior work-related permanent impairments affecting the same area of the body" from a work-related permanent impairment. The policy sets out that, in order to be factored out, a condition must be capable of being rated under the AMA Guides. The Vice-Chair determined that the policies do not contain language of significance which would indicate that their intent is to preclude pre-existing asymptomatic pre-existing conditions from being factored out from a worker's whole person impairment rating, nor are there provisions contained in the policies which would indicate that their intent is to preclude deductions for asymptomatic pre-existing conditions. The Vice-Chair found that the NEL Clinical Specialist correctly followed the three-step process.
The Vice-Chair emphasized that the worker's compensation system is not intended to grant entitlement and benefits to workers for pre-existing conditions for which entitlement has not been granted. It was also noted that entitlement to osteoarthritis and a meniscal tear were not before the Vice-Chair in this appeal.
As a result of the foregoing, the Vice-Chair found that the NEL Clinical Specialist correctly applied Table 40 of the AMA guides in recognizing that the worker did not have entitlement for left knee osteoarthritis and/or a meniscal tear, and correctly deducted the impairment rating for these conditions from the worker's whole person NEL award. The Vice-Chair relied on Tribunal case law in clarifying that the 0% impairment rating for a meniscal tear refers to the severity of the condition, as opposed to whether or not the condition was a pre-existing asymptomatic condition, and found that it would be inappropriate to assign a 0% impairment rating for arthritis or a meniscal tear on this basis. The Vice-Chair stated that Table 40 requires an assessor to consider the available medical evidence, and determine, based on the objective clinical evidence, which disorder(s) exist. Furthermore, while some disorders listed in Table 40 require evidence of loss of strength or instability, other disorders, such as arthritis and a meniscal tear, do not.
The Vice-Chair noted that the process outlined above is consistent with OPM Document No. 18-05-03 and the rationale behind Decision No. 297/19, which outline that this approach is consistent with the principles of tort law and Board policy which seek to prevent a worker from being placed in a better position than he or she would have been in "but for" the work related accident.
With respect to the applicability of the thin skull doctrine, the Vice-Chair referenced the decision of Blackwater v. Plint, where the Court emphasized that a plaintiff is entitled only to be compensated for loss caused by the actionable wrong, as the "essential purpose and most basic principle of tort law" is to prevent a plaintiff from being placed in a better position than he or she would have been in had the tort not been committed. The Vice-Chair concluded that Board policy is consistent with the law of damages in Canada, and the reduction of an impairment to account for pre-existing damage or loss, which in this case were caused by non-compensable factors, is not inconsistent or contrary to the thin skull principle. The Vice-Chair stated that as a condition does need not be symptomatic to attract entitlement or compensation within the workers' compensation scheme or in common law, the thin skull doctrine cannot be used as justification for not deducting asymptomatic pre-existing conditions from a worker's whole person impairment rating.