An employee trips over a piece of equipment at work and injures his knee. After reviewing the history, medical records, and mechanism of injury, a Qualified Medical Evaluator concludes, within reasonable medical probability, that the work incident caused the knee injury.
The applicant undergoes treatment and eventually reaches Maximum Medical Improvement (MMI), with permanent disability remaining. The QME determines that only a portion of that permanent disability is attributable to the industrial injury, while the remainder is attributable to a preexisting condition.
At first glance, those conclusions might seem inconsistent. If the work incident caused the injury, why isn’t the entire resulting disability considered industrial?
Two Distinct Questions
The distinction between causation of an injury and apportionment of permanent disability was addressed directly by the Workers’ Compensation Appeals Board in Escobedo v. Marshalls. The Board explained that apportionment is based on the causation of permanent disability, not simply the causation of the original injury, and that the factors contributing to each may differ.
It can help to think of the analysis as two separate tracks.
Track One: What caused the injury?
This question focuses on the injury itself. What happened? What condition resulted? Did the employment event cause or contribute to the applicant’s injury?
This analysis may occur before the applicant reaches MMI. It addresses the relationship between the work event and the injury, rather than assigning percentages to the causes of permanent disability.
Track Two: What caused the permanent disability?
This question becomes central when the applicant’s condition has stabilized and permanent disability is being evaluated. The focus shifts to the permanent disability being evaluated: What caused it, and what portion is attributable to the industrial injury versus other factors?
Under Labor Code §4663, apportionment of permanent disability is based on causation. The evaluator must address the approximate percentage of permanent disability caused by the direct result of the industrial injury and the percentage caused by other factors, both before and after the injury, including prior industrial injuries.
Returning to the Knee Injury
Consider the applicant who tripped over equipment at work. The fall was witnessed, he promptly sought medical attention, and the medical evidence supports the conclusion that the incident caused his knee injury. The QME may reasonably determine that the injury is industrial.
After treatment, the applicant reaches MMI but continues to have limited range of motion in the knee. The QME must now consider what caused the permanent disability that remains.
Suppose the applicant had degenerative changes in the knee before the fall due to a prior ACL injury sustained in sports decades before, and already had knee pain and decreased range of motion. A preexisting condition like this may contribute to the permanent disability that remains. However, its presence does not automatically mean the original injury was nonindustrial, nor does the diagnosis alone establish that the condition caused permanent disability. It is the responsibility of the QME to consider the medical evidence and determine whether, and to what extent, the preexisting condition contributed to the permanent disability at MMI.
Why the Distinction Matters
The QME must consider how that evidence relates to each question rather than carrying the conclusion on injury causation directly into the permanent disability analysis.
A preexisting diagnosis, by itself, does not establish apportionment. The evaluator must explain how and why the condition caused or contributed to permanent disability. As Escobedo makes clear, an apportionment opinion must be supported by substantial medical evidence and include reasoning that connects the identified factors to the permanent disability.
The issue is not simply whether another condition exists. It is whether the evidence supports the conclusion that the condition contributed to the permanent disability being evaluated.
Asking the Right Questions
Keeping these two causation questions separate requires a clear understanding of the applicant’s medical history and the evidence available for review. Records from before the injury, the initial evaluation, subsequent treatment, and the MMI examination may each help answer a different part of the analysis.
Identifying relevant records, developing an accurate history, and recognizing missing information can help ensure that both causation questions are fully explored. This is one reason medical-legal support can be valuable. OrthoLegal assists QMEs with these aspects of the evaluation, as well as report support and editing, helping evaluators identify the issues that need to be addressed and develop clear, well-supported opinions.
Two Questions, One Evaluation
Causation of the injury and causation of permanent disability are closely related, but they are not interchangeable.
A QME may determine that a workplace event caused an injury while also finding that other factors contributed to the permanent disability that remains. Those conclusions are not necessarily inconsistent; they address different causal relationships.
By answering each question separately and explaining how the medical evidence supports each conclusion, a QME provides a more complete understanding of the nature of the injury as well as the claim.