THE SHORT ANSWER
Apportionment is to permanent disability — not to pathology, not to imaging findings, not to risk factors, and not to history. Under Escobedo v. Marshalls (WCAB en banc), a physician must explain the how and why. A report that names a condition — arthritis, degeneration, diabetes, age, obesity, a prior injury — and attaches a percentage without reasoning is not substantial evidence, and it cannot support an apportionment finding.
On this page
What follows is what §§ 4663 and 4664 actually require, the four factual questions that decide most apportionmentApportionment Dividing permanent disability between industrial and non-industrial causes. It is to disability, not to findings on an image. fights, the argument to expect for each injury, the three rules that limit apportionment — including the one that has been narrowed — and what to do about a bad opinion before discovery closes.
What the statute requires
The law makes apportionment based on causation. A physician who addresses permanent disabilityPD Permanent Disability. Compensation for lasting impairment. A different and much lower weekly rate — 2026 maximum $290/week. must make an apportionment determination and must state what approximate percentage of the permanent disability was caused by the direct result of the injury, and what approximate percentage was caused by other factors, including any prior industrial injury. And the physician must be able to say that the opinion is held to a reasonable medical probability, with the reasoning stated.
§ 4664 — WHAT THE EMPLOYER OWES
The employer is only liable for the percentage of disability directly caused by the industrial injury.
§ 4664(b) — THE CONCLUSIVE PRESUMPTION
Where there is a prior award of permanent disability, that disability is conclusively presumed to still exist — a real and often harsh rule in a worker with a documented prior award. It applies to a prior award, not to a prior injury.
The four questions that decide it
- Were you doing your full job the day before? — A worker performing full duties, without restriction, accommodation, or complaint, had no disability from the pre-existing condition — whatever an image showed. This is the strongest single fact in most apportionment fights, and it is a factual question you can answer.
- Did the evaluator review your pre-injury records? — An opinion apportioning to a prior condition, written by a physician who reviewed nothing from before the injury, has no factual basis for the percentage. Ask what records were reviewed — the report has to list them.
- Does the report tie the prior condition to this disability? — Be careful here: under City of Petaluma v. WCABWCAB Workers’ Compensation Appeals Board. The court system that decides these cases. 23 district offices statewide. (Lindh) (2018) 29 Cal.App.5th 1175, a pre-existing condition that never disabled anyone can support apportionment — prior disability is no longer a prerequisite. What § 4663 still requires is causation of this disability, proved by substantial medical evidence. A report that names a degenerative finding and stops has not done that.
- What supports this percentage rather than another one? — Why 50% and not 20%? If the report cannot answer that with reasoning tied to the record, it does not satisfy EscobedoEscobedo The en banc decision requiring an apportionment opinion to explain how and why. A percentage without reasoning is not substantial evidence..
The arguments you should expect
| INJURY · THE ARGUMENT | WHAT ANSWERS IT |
|---|---|
| Low back — degenerative disc disease | Degeneration is near-universal and mostly asymptomatic; apportionment is to disability |
| Shoulder — asymptomatic cuff tears exceed 50% prevalence over 60 | Their own literature says those people are not disabled |
| Knee — arthritis and body weight | Real risk factors — still must explain a percentage of disability |
| Carpal tunnel — diabetes, thyroid, obesity, non-work keyboard use | Risk factors are not disability |
| Hearing loss — presbycusis | The audiogram configuration distinguishes them — noise notch at 4–6 kHz |
| Brain injury — prior concussion, alcohol, ADHD | A concussion that resolved caused no disability |
| Psychiatric — prior treatment, personal stressors | Different statutory framework — see § 3208.3 |
Three rules that limit apportionment
MEDICAL TREATMENT CONSEQUENCES — HIKIDA, AND HOW IT WAS NARROWED
Under Hikida v. WCAB (2017), where industrial medical treatment itself causes permanent disability — a failed surgery, a post-operative complication, a nerve injury during a procedure — that disability is industrial. But County of Santa Clara v. WCAB (Justice) (2020) 49 Cal.App.5th 605 holds that it “precludes apportionment only where the industrial medical treatment is the sole cause of the permanent disability.” Where pre-existing pathology also contributes, §§ 4663 and 4664 apportionment still applies.
THERE IS NO SUCH THING AS “VOCATIONAL APPORTIONMENT”
In Nunes v. State of California, Dept. of Motor Vehicles (WCAB en banc, June 22, 2023), the Board held that only reporting physicians may determine apportionment, and that there is “no statutory provision for ‘vocational apportionment.’” A vocational expert cannot substitute a 0% vocational apportionment for a physician’s medical apportionment. Nunes II affirmed it.
§ 4664(b) REQUIRES AN ACTUAL PRIOR AWARD
A prior claim that settled by Compromise and ReleaseC&R — Compromise and Release A lump sum that closes future medical treatment permanently. without an award of permanent disability is not a prior award. This gets asserted more often than it applies.
What to do about a bad apportionment opinion
- Read the paragraph — It is usually short, and it usually states a conclusion rather than reasoning. That is the defect.
- Check what records were reviewed — If the list does not include pre-injury records, say so.
- Get your own pre-injury records — Primary care, urgent care, chiropractic, anything paid through your own health insurance. Their absence of complaint is evidence.
- Document the full duty history — Job description, performance record, attendance, and the absence of any accommodation.
- Raise it before the mandatory settlement conferenceMSC Mandatory Settlement Conference. Where most cases end — and where discovery closes. — Discovery closes there, and a supplemental report or a deposition of the evaluator obtained afterward is generally inadmissible.
Frequently asked questions
What is apportionment?
Dividing permanent disability between industrial and non-industrial causes. The employer pays only for the industrial share.
They apportioned 50% to arthritis. Can they do that?
Only with an explanation. Under Escobedo the physician must explain how and why the non-industrial factor caused that share of the disability. A percentage without reasoning is not substantial evidenceSubstantial evidence The standard a medical opinion must meet to support a finding..
I had a prior injury.
Under Lindh, a condition that never disabled you can support apportionment — that is the law, and we will not tell you otherwise. What the defense must prove is that it caused part of this disability, with reasoning that satisfies Escobedo. A prior award is different again — the law conclusively presumes that disability still exists.
My surgery made me worse.
Under Hikida, disability caused by industrial medical treatment is industrial and generally not apportionable. But Hikida has been cut down, and the site that does not say so is out of date. In County of Santa Clara v. WCAB (Justice) (2020) 49 Cal.App.5th 605 the Court of Appeal held that Hikida “precludes apportionment only where the industrial medical treatment is the sole cause of the permanent disability.” Sole cause is a demanding test, and the rule is much narrower than it is usually described.
Can a vocational expert change the apportionment?
No. Nunes holds that only reporting physicians determine apportionment, and that “vocational apportionment” is not a valid legal theory.
Sources
Labor Code § 3208.3§ 4663§ 4664§ 5502(d)(3)Escobedo v. Marshalls (WCAB en banc)City of Petaluma v. WCAB (Lindh) (2018) 29 Cal.App.5th 1175Hikida v. WCAB (2017) 12 Cal.App.5th 1249County of Santa Clara v. WCAB (Justice) (2020) 49 Cal.App.5th 605 [85 Cal.Comp.Cases 467]Nunes v. State of California, Dept. of Motor Vehicles (WCAB en banc, June 22, 2023) and Nunes II.
General information about California law, not legal advice about your case.
Reviewed by Jamey Teitell, Partner & Trial Attorney · Last reviewed
Law Offices of Solov & Teitell, APC · (213) 380-9310
Printed from https://www.solovteitell.com/workers-compensation/apportionment/ · Last reviewed