Apportionment Fight Case Study | Degenerative Imaging in California Comp

What does Labor Code 4663 require from a doctor?

Labor Code 4663 requires apportionment to be based on causation, with a doctor explaining the approximate work and non-work shares and the medical reason for the split.

Apportionment is a money issue. Each percentage assigned to non-work causes reduces the permanent disability paid by the employer. That is why a vague QME report can cause real harm.

Labor Code 4663 says apportionment must be based on causation. Labor Code 4664 says the employer is liable only for the disability caused by work. Those rules do not let the carrier guess. They require a medical explanation.

The verified framework for this fight is simple. Escobedo v. Marshalls is a WCAB en banc decision. It allows apportionment to asymptomatic degeneration only when the doctor gives substantial evidence showing the how and why. A bare reference to imaging is not enough.

How was the QME opinion challenged?

The challenge focused on the gap between imaging and disability, pressing the QME to explain whether the worker had actual impairment before the industrial injury.

The supplemental request did not argue that the MRI was fake. It asked the right question. What functional disability existed before the work injury? Did the worker lose time? Did the worker have restrictions? Did any doctor rate permanent impairment before the industrial event?

If the answer was no, the QME needed to explain why silent imaging deserved half the rating anyway. The report also had to explain why the job injury was not the full cause of the lasting work limits.

That approach narrowed the issue for the WCAB. The dispute was not about whether the spine showed wear. It was about whether the carrier had substantial medical evidence for the proposed split.

What changed the settlement posture?

Once the unsupported split was attacked, the carrier could no longer value the file as a routine degeneration case with a simple reduced rating.

The value of an apportionment challenge is often indirect. It changes the risk on both sides. A carrier that expected to pay half the rating now has to face the possibility of paying the full rating, future care, and any delayed amounts tied to the wrong valuation.

The worker also needed a clear record for trial. If the QME repaired the report with real reasoning, settlement could still follow. If the QME could not explain the split, the worker had a stronger path to reject the apportionment.

The final resolution preserved the higher award position. The specific outcome depended on the medical record, the QME testimony, the disability rating, and the settlement posture.

Why was accepting the first rating risky?

Accepting the first reduced rating would have locked in the carrier's view before the QME explained whether silent degeneration had caused real disability.

The first number was not the final answer. It was a medical opinion that could be tested. The worker needed to know whether the QME had reviewed the full job history, the old medical file, the lack of prior work loss, and the actual onset of symptoms.

A quick settlement would have ended that inquiry. It would have treated the old scan as proof by itself. That was the risk. Once a settlement closes, the worker may not get another chance to prove the full disability.

The better path was careful and narrow. Ask for the missing explanation. Compare the QME's split with the worker's history. Show that the worker had been doing the job before the industrial injury. Then value the case after the medical record was complete.

This approach did not promise a full win. It gave the worker a fair record. In an apportionment case, a fair record can change the money because the difference between a reduced rating and the full rating is often the core value of the file.