Understanding Causation

Tennessee-specific Definition of "Injury"

The Workers’ Compensation law changed significantly regarding injuries that occurred on or after July 1, 2014. One of the changes was the new and different legal criteria in the physician's assessment of the medical aspects of their opinion on causation. According to the Tenn. Code Ann. Sect. 50-6-102(12):

"Injury" and "personal injury" mean an injury by accident, a mental injury, occupational disease including diseases of the heart, lung and hypertension, or cumulative trauma conditions including hearing loss, carpal tunnel syndrome or any other repetitive motion conditions, arising primarily out of and in the course and scope of employment, that causes death, disablement or the need for medical treatment of the employee; provided, that:

• A. An injury is "accidental" only if the injury is caused by a specific incident, or set of incidents, arising primarily out of and in the course and scope of employment, and is identifiable by time and place of occurrence, and shall not include the aggravation of a preexisting disease, condition or ailment unless it can be shown to a reasonable degree of medical certainty that the aggravation arose primarily out of and in the course and scope of employment;
• B. An injury "arises primarily out of and in the course and scope of employment" only if it has been shown by a preponderance of the evidence that the employment contributed more than fifty percent (50%) in causing the injury, considering all causes;
• C. An injury causes death, disablement or the need for medical treatment only if it has been shown to a reasonable degree of medical certainty that it contributed more than fifty percent (50%) in causing the death, disablement or need for medical treatment, considering all causes;
• D. "Shown to a reasonable degree of medical certainty" means that, in the opinion of the physician, it is more likely than not considering all causes, as opposed to speculation or possibility;
• E. The opinion of the treating physician, selected by the employee from the employer's designated panel of physicians pursuant to § 50-6-204(a)(3), shall be presumed correct on the issue of causation but this presumption shall be rebuttable by a preponderance of the evidence.

How to Address Causation Issues

If you, the physician, are asked to explain and issue a report regarding causation, the following information may be helpful: 

1. 1. Description of the diagnosis (or diagnoses) both in medical and lay terms, including the appropriate ICD code.
2. A complete and detailed description of the injury including the mechanism, time, place, and (in the case of cumulative-trauma conditions) number, duration or frequency.
   • For injuries with major violence, causation is rarely in dispute, and the statement of the mechanism of injury is usually sufficient. For example: “sustained a fracture to the calcaneus from a 20-foot fall from a roof.”
3. For cases in which the incident would not be judged to injure most people, consider whether symptoms, pre-existing conditions, co-morbidities, prior injuries, previous surgeries, or events unrelated to employment might be important contributing factors.
   • If those factors existed without a need for treatment but for the work injury, an appropriate medical opinion may be that the work injury is more than 50% responsible for the need for treatment. Thus, a functional but asymptomatic arthritic knee that is injured at work may result in an opinion based on an assessment of all causes that the work incident is more than 50% responsible for the need for treatment. The Court will apply the legal standard for the ultimate decision on compensability, considering the medical proof and other facts.
   • In the absence of other contributing factors, consider whether the start of symptoms while working can answer the question of “why” the symptoms started in relationship to work—the mechanism of injury—not just “when.” For example, a first episode of angina that occurred at work (“when”) does not necessarily mean that the work caused the later-diagnosed coronary artery disease (“why”).
4. Consider whether the need for treatment was an aggravation of a preexisting condition.
   • Aggravation means an intensification or worsening of a preexisting disease, condition or ailment, permanent or not, that contributes more than 50% in causing death, disability, or the need for medical treatment. An “aggravation” does not require a permanent change or a permanent worsening of a condition.
5. When all this information is taken together, is it more likely than not, to a reasonable degree of medical certainty, that this incident was the cause of the need for treatment?
   • For example, consider the treatment for diabetes discovered during treatment of a fractured ankle. Would the need for the long-term treatment of diabetes be, more likely than not, caused by the fractured ankle?

Medical Opinion (not Legal Determination)

Importantly, you are not being asked to make a legal determination of whether the injury was compensable. The physician's role is to provide a medical opinion, based upon current medical evidence: is it more likely than not, considering all causes, as opposed to speculation or possibility, that the injury contributed more than 50% in causing the death, disablement or need for medical treatment?

Purpose and Impact

These changes in the definition of an injury and aggravation are significant in the interpretation of the workers’ compensation law. It is intended to limit misunderstandings and resolve disputes as early in the process as possible. The physician's understanding is critical. If you have questions about these issues while treating Tennessee injured workers, please contact the Bureau of Workers’ Compensation Medical Director at 615-532-8700 or Robert.B.Snyder@tn.gov.