Pre-Existing Conditions & Workers Comp: What You Need to Know

The Big Lie: "Pre-Existing Means No Coverage"

Let's start with the most important truth: having a pre-existing condition does not disqualify you from workers' compensation benefits in California.

Read that again. Write it down. Remember it when the insurance adjuster tells you otherwise.

California law recognizes reality—many workers have prior injuries, age-related degeneration, or chronic conditions. What matters is whether your job made it worse, not whether you had a problem before.

California's Aggravation Rule

Labor Code §4663 establishes a critical principle: if industrial (work-related) factors combine with non-industrial (pre-existing) factors to cause disability, you're still entitled to benefits.

In practical terms, this means:

• You had mild arthritis in your knee before this job → Your job's repetitive squatting made it severe → Covered
• You had degenerative disc disease in your back → Lifting at work caused a herniation → Covered
• You had carpal tunnel symptoms years ago → Typing at this job worsened it requiring surgery → Covered
• You have diabetes → Your warehouse job's poor climate control caused heat stroke → Covered

The question isn't "did you have problems before?" It's "did work make it worse, accelerate it, or light it up?"

Common Pre-Existing Conditions and Workers' Comp

Let's address specific scenarios:

Degenerative Disc Disease

Nearly everyone over 40 has some disc degeneration visible on MRI. Insurance companies act like this proves your back pain isn't work-related. Wrong.

The Reality:

• Asymptomatic degeneration (visible but painless) doesn't matter
• If you were working fine despite degeneration, and work caused pain/herniation, you're covered
• Work can "light up" degenerative changes that were previously asymptomatic
• Lifting, twisting, or trauma can turn mild degeneration into severe disability

Arthritis

Osteoarthritis is age-related wear and tear. It's also extremely common. Having arthritis on X-rays doesn't preclude workers' comp.

What's Compensable:

• Mild arthritis → heavy use at work → severe arthritis requiring joint replacement
• Manageable arthritis → workplace fall → acute worsening
• Arthritis in one joint → compensatory overuse of other joints → new injury

Prior Injuries to the Same Body Part

Maybe you hurt your shoulder five years ago, recovered, and returned to normal function. Then this job re-injures it. Still covered.

Key Factors:

• Were you fully functional before this job? (If yes, strong case)
• Did a specific work incident cause new damage? (Acute injury vs. gradual)
• Does the new injury exceed what existed before? (MRI comparison helps)

Obesity

Insurance companies love to blame weight. "Your knee hurts because you're overweight, not because of work." This is medical nonsense used to deny claims.

The Truth:

• Obesity may contribute to joint wear, but it doesn't cause acute injuries
• If your job requires excessive standing, kneeling, or climbing—and your knees fail—that's industrial
• Weight alone doesn't cause rotator cuff tears, herniated discs, or carpal tunnel
• California allows apportionment (discussed below), but doesn't allow total denials based on obesity

Diabetes

Diabetics can develop neuropathy (nerve damage) independent of work. But work can also cause or worsen nerve issues.

Covered Scenarios:

• Repetitive strain causing carpal tunnel (even if you have diabetic neuropathy elsewhere)
• Workplace heat exposure causing diabetic complications
• Falls or accidents aggravating diabetic foot problems

Previous Surgeries

Had a prior back surgery? Shoulder surgery? That doesn't immunize you from new work injuries.

Analysis:

• If you recovered from prior surgery and were working normally, new injury is compensable
• If surgery left you with permanent restrictions and work exceeded those restrictions, you're covered
• New trauma to previously-surgized areas often causes more severe injury (worth more, not less)

Apportionment: The Real Issue

Here's where pre-existing conditions actually matter: not in whether you're covered, but in how much you recover.

What Is Apportionment?

Apportionment divides your permanent disability into percentages:

• What percentage is caused by this job? (Industrial)
• What percentage existed before or is unrelated? (Non-industrial)

You only receive workers' comp benefits for the industrial percentage.

Example: Back Injury with Degeneration

Burden of Proof

Here's the critical part: under Labor Code §4664, the insurance company must prove apportionment. They can't just claim "it's all pre-existing" without medical evidence.

They need:

• Medical records showing prior treatment for the same body part
• Imaging comparisons (old MRI vs. new MRI)
• Expert medical opinions quantifying non-industrial vs. industrial causation

If they can't prove a specific percentage, you get 100% credit for industrial causation.

How Insurance Companies Abuse the Pre-Existing Defense

Tactic 1: Claiming Normal Aging Is a "Condition"

Everyone's spine degenerates with age. Everyone develops some arthritis. Insurance companies try to classify normal aging as a disqualifying "pre-existing condition."

Counter:

• Asymptomatic degeneration isn't a condition—it's aging
• If you functioned normally before this job, aging doesn't explain sudden disability
• Expert testimony distinguishes normal aging from industrial acceleration

Tactic 2: Digging Up Ancient Medical Records

You mentioned knee pain to your doctor 10 years ago. The insurance company subpoenas those records and claims your current injury is "just the same old problem."

Counter:

• Show you recovered and worked without restriction for years
• Prove the current injury is distinct (new MRI findings, different mechanism)
• Demonstrate you were asymptomatic immediately before this job

Tactic 3: Exaggerating Apportionment Percentages

Their medical examiner claims 90% non-industrial, 10% industrial—with minimal justification.

Counter:

• Hire your own expert who provides detailed apportionment analysis
• Cross-examine their doctor on the basis for their opinion
• Show the doctor is a hired gun who always favors insurance companies

Tactic 4: Selective Record Review

They focus on old records showing problems while ignoring recent records showing you were functional.

Counter:

• Provide complete medical timeline showing recovery and normal function
• Get employer evaluations proving you met all job requirements pre-injury
• Obtain testimony from coworkers that you worked without limitations

Proving the Work Connection

To maximize your recovery despite pre-existing conditions, you must prove:

1. You Were Functional Before This Job

Evidence includes:

• Job performance reviews showing no limitations
• Attendance records (no excessive medical leave)
• Testimony from supervisors and coworkers
• Personal activity records (hobbies, sports, physical activities you could do)

2. Work Demands Exceeded Your Capacity

Show your job involved:

• Repetitive motions beyond normal activity
• Heavy lifting, awkward positions, or extreme force
• Prolonged standing, kneeling, or other stressors
• Specific incident that triggered new injury

3. Medical Causation Links Work to Injury

Your treating doctor must write a report explaining:

• How your job duties caused or worsened the condition
• Why work is the predominant cause (if cumulative trauma)
• What percentage is industrial vs. non-industrial (apportionment)

4. Timing Supports Work Causation

Document:

• Symptoms began or worsened after starting this job
• Direct temporal relationship between work activities and pain
• No intervening non-industrial causes

Strategies to Maximize Recovery

1. Get Detailed Medical Opinions

Don't accept vague medical reports. Your doctor should specifically address:

• "The patient had mild degenerative changes that were asymptomatic"
• "Work activities caused acute herniation superimposed on degeneration"
• "I apportion 80% industrial causation, 20% non-industrial"
• "Without the industrial injury, patient would have remained functional"

2. Obtain Comparative Imaging

If you have old X-rays or MRIs, compare them to current imaging. This objectively shows:

• New findings not present before
• Progression beyond what aging alone would cause
• Acute changes vs. chronic degeneration

3. Emphasize Sudden Change

If you went from working fine to disabled, that's powerful evidence work caused the problem:

• "I worked this job for 5 years with no problems, then suddenly couldn't continue"
• "The day of the lifting incident, everything changed"
• "Before this job, I played basketball twice a week—now I can't walk without pain"

4. Use Vocational Evidence

Vocational experts can testify:

• Your job demands exceeded typical activity levels
• Pre-existing conditions didn't prevent you from working before this job
• The industrial injury caused loss of earning capacity beyond any prior limitation

Special Situations

Multiple Employers

What if you had the same injury at previous jobs? California allows claims against multiple employers, or you can elect which claim to pursue. An attorney helps navigate this complexity.

Successive Injuries

Injured the same body part at Job A, recovered, then injured it again at Job B? Both claims may be valid, but apportionment gets complicated. Job B's insurer will argue Job A caused most of the disability.

Labor Code 4663(b): "Directly Caused"

For injuries after 2005, apportionment only applies to disability "directly caused" by factors other than work. This is a higher standard than mere contribution—it limits aggressive apportionment defenses.

Real-World Examples

Frequently Asked Questions

The Bottom Line on Pre-Existing Conditions

Don't let insurance companies scare you with pre-existing condition defenses. In California, these defenses rarely result in total denials. At worst, they reduce your settlement through apportionment—but you still recover substantial benefits.

The keys to success:

1. Document that you were functional before this job
2. Prove your work duties caused or worsened the condition
3. Get strong medical opinions on causation and apportionment
4. Fight aggressive apportionment with your own experts
5. Hire an attorney who understands how to combat these defenses

Remember: you don't need a perfect medical history to deserve workers' compensation. You just need to prove work made you worse—and California law is on your side.