Common Objections to Workers’ Comp Reports: Apportionment

This article is part of a series on the top reasons why insurance carriers object to a workers’ compensation report and return it to the medical practice unpaid. This article is intended for medical providers, administrative staff, office managers, as well as claims adjusters.

Welcome to the final in our series of posts about red flags in impairment reports, and how to ensure that your reports are not objected to by an insurance company. In our previous posts, we have covered incomplete history of symptoms, unchecked Activities of Daily Living (ADLs), accounting for prior injuries, incomplete examination, and complications with diagnostic tests.

In a perfect world, the long road of a workers’ compensation claim would end in a healthy patient with a 0% WPI, an fairly compensated primary treating physician, a satisfied claims adjuster, and no involvement with an attorney. But it’s rarely this simple.

Apportionment is an attempt to objectify something that cannot be measured with tools, which opens up the possibility for disagreement. As we’ve learned from our other blog posts in this series, disagreements between PTPs and the employers’ insurance can cause slowed claims, delayed treatment, and could result in the need for an attorney.

Reason #6: Poorly Determined Apportionment

In plain English: when the physician determines the apportionment, they are deciding how much of the patient’s disability is caused by the work injury, and how much of the disability is caused by everything else.

As you can imagine, an injury’s apportionment is a significant factor when the insurance carrier needs to figure out how much of the patient’s symptoms they are responsible for. The workers’ comp insurance carrier wants to pay for the treatment for symptoms that are related to the work injury, but does not want to be financially responsible for treating symptoms that are not caused by the work injury.

Determining an injury’s apportionment using science and evidence is no small task. As a result, many providers simply guess when it comes to apportionment.

Here are a few key facts about apportionment:

  • Apportionment is applied to the patient’s permanent disability, rather than their impairment rating. Remember, the impairment rating is used to calculate the permanent disability.
  • A physician’s apportionment determination must be based on accepted medical knowledge. Even though guessing an injury’s apportionment is common practice, apportionment should be based on evidence.
  • Any medical conditions that result in permanent impairment according to The AMA Guides are, by definition, “accepted medical knowledge.”


Here’s an example scenario based on common events. Let’s imagine there’s a woman named Lyanna who worked in a warehouse.

Lyanna developed arthritis in her spine. As time went on and the arthritis progressed, her range of motion was limited, but she was able to do her job. The impact that her arthritis was having on her activities of daily living was never documented by her doctor, and the range of motion of her spine was never measured.

Fast forward a few years: on the day after the Superbowl, Lyanna showed up for work only to find that her entire crew called in sick. The timing could not have been worse: there were 40 pallets that needed to go out by the end of the day. Lyanna went to work.

Twenty pallets in, began to feel awful pain in her lower back. She realized that she needed to see a doctor immediately. She contacted her manager, who sent her off to a primary treating physician. Because the injury apparently happened at work, it was a workers’ compensation case.

At the clinic, Lyanna told her new workers’ comp physician about how she hurt her back lifting pallets. She also told him about her history of arthritis.

After performing an X-ray, the physician realized that Lyanna had a slipped disk in her lumbar spine. He also noted that her arthritis was impacting the same body part that had been injured at work.

Lyanna returned to the workers’ comp physician for follow up visits. After a year of treatment and modified work duty, Lyanna had improved, but she still had a limited range of motion when bending over and had to perform modified duty at work.

Eventually, the physician determined that she had reached MMI (Maximum Medical Improvement)—in other words, she was not going to get any better.

Of course, this meant it was time to write the PR-4 Permanent & Stationary impairment report. Lyanna went to the doctor for one final visit. The doctor gathered all the necessary information, and started writing the impairment report.

Writing the report

To write Lyanna’s PR-4 report, the doctor used the template found on the California Department of Industrial Relations website. He came to the section for Apportionment, which contains the following two yes/no questions:

Is the permanent disability directly caused, by an injury or illness arising out of and in the course of employment?

Is the permanent disability caused, in whole or in part, by other factors besides this industrial injury or illness, including any prior industrial injury or illness?

Lyanna’s permanent disability was partially caused by the work-related injury, but based on past testing, the physician also knew that part of her disability was caused by her arthritis. Therefore, the physician answered “Yes” to both questions.

Beneath these questions, the DIR’s PR-4 report template reads:

If the answer to the second question is “yes,” provide below: (1) the approximate percentage of the permanent disability that is due to factors other than the injury or illness arising out of and in the course of employment; and (2) a complete narrative description of the basis for your apportionment finding. If you are unable to include an apportionment determination in your report, state the specific reasons why you could not make this determination. You may attach your findings and explanation on a separate sheet.

Since Lyanna’s doctor answered “Yes” to question #2, he also needed to indicate what percentage of Lyanna’s permanent disability was caused by the work injury and other factors—as well as a complete explanation that justifies that determination.

Here’s what the PTP wrote in the report.

Approximately 75% of the permanent disability is caused by this industrial injury. The other 25% of the permanent disability is apportioned to the pre-existing condition of mild arthritis of the lumbar spine.

But that’s not the end of the provider’s answer. He still needed to “include a complete narrative description of the basis for [his] apportionment finding.” Where did the 50% come from, and why?

Well, if Lyanna’s provider was like most providers (very busy), he probably just sort of guessed.

A nice round number, but backed by the books

But, if Lyanna’s provider wanted to do a thorough job on the apportionment, then here’s how his process might have gone: based on Lyanna’s X-rays and the radiologist’s report, he knew her arthritis was “mild” in severity. Arthritis is commonly called either “mild”, “moderate”, or “severe”—and although these terms may have their gray areas, he believed that very few radiologists would use the term “moderate” to describe Lyanna’s arthritis.

Next, the provider found a peer-reviewed case study that described how “mild” arthritis of the lumbar spine impacted patients’ activities of daily living and range of motion. Based on this piece of accepted medical literature, and comparing it to the impact that Lyanna’s back was having on her life, it was clear that a “mild” case of arthritis would not describe all of Lyanna’s disability. In other words, it was unreasonable to think that her arthritis alone was responsible for the entirety of her disability.

Then, the provider found another study about herniated-discs, which was Lyanna’s work injury.

Using these studies and his measurements of Lyanna’s injury, the provider concluded that 75% of Lyanna’s disability was caused by her work injury, while 25% should be apportioned to the arthritis.

These nice round numbers are a good indicator that the provider was using more art than science. However, by examining medical literature and explaining his thought process, Lyanna’s provider’s apportionment determination was already much better than most apportionment determinations out there. If an attorney or a QME were to dispute his apportionment, then they would need to analyze Lyanna’s provider’s reasoning and find a flaw.


A thorough explanation of how to calculate truly accurate apportionment is beyond the scope of this blog post–the subject deserves an entire book.

But if you’re a provider and you’re determining apportionment, here’s the boxes that need to be checked:

  • Base the apportionment on objective measurements. That means measuring the range of motion and performing other tests.
  • Reference accepted medical literature.
  • Note the diagnoses of the work-related injury and other diagnoses that are relevant to the injury.
  • Include all relevant past medical history and diagnostic testing in the impairment report.
  • Be prepared to defend your reasoning.


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