Apportionment and Pre-Existing Conditions in California Workers’ Compensation

Apportionment in California workers' compensation splits up the causes of an injured worker's permanent disability.

Permanent disability for each injured part of body may be caused by the work injury and pre-existing medical conditions.

A pre-existing condition can be a:

  • non-work-related injury
  • non-work-related medical condition
  • previous work injury

Apportionment reduces a California injured worker's permanent work disability. This reduces the cash value of his or her claim.

There is also apportionment when an injured worker has two or more work injuries at the same time. Each injury is given a separate percentage value. This has a lower dollar value than if the injuries are combined.

A doctor's permanent and stationary report is not valid evidence without a discussion of apportionment.

Apportionment is calculated after:

  • a doctor provides a rating of the injured body part using the American Medical Association Guides to the Evaluation of Permanent Impairment, 5th Edition
  • the doctor's rating is translated into a permanent disability rating using the Permanent Disability Rating Schedule

Workers' compensation must pay for all medical care even if there is apportionment to a pre-existing condition.

In this article, our California personal injury attorneys will explain:

doctor examining xray apportionment pre-existing conditions workers' comp california
Apportionment is the process of dividing the permanent disability of an injured worker between work-related and non-work-related causes.

1. What is apportionment?

Apportionment is the process of separating an injured worker's work permanent disability due to work from a disability that comes from a source outside of work.

When an injured worker's condition has stabilized, he or she will receive a rating for any permanent loss of ability or function. But if some of the loss of ability or function is caused by something that is unrelated to work, that amount will reduce the work permanent disability of the worker's injury.

1.1. Prior non-work-related injury

If a portion of permanent disability is not caused by work, the employer is not responsible for it.1 It is not part of the value of an injured worker's case.

Example: Jerry injures his left knee at work. After having arthroscopic knee surgery and physical therapy, Jerry's condition stabilizes.

Jerry's treating doctor evaluates Jerry's knee and gives him 12% impairment for his knee. But when the doctor first saw Jerry for his knee injury, Jerry said he injured his left knee playing high school football and has had stiffness in his knee ever since.

Because Jerry had a prior knee injury, the doctor apportions 20% of Jerry's current knee condition to his prior football injury.

The employer is only responsible for the remaining 80% of the injury. Of the 12%, the employer is responsible for 9.6%.

1.2. Combination of work and non-work injuries

An employee does not need to have a prior injury for there to be apportionment. A work activity and a non-work activity can combine to cause an injury.

Example: Alicia works as a graphic designer and plays tennis twice a week. Over time she injures her right elbow. She files a cumulative trauma claim for a work injury.

Her doctor finds that Alicia's elbow impairment of 7% is 50% from her graphic design work and 50% from weekly tennis. The employer is only responsible for half of her disability.

1.3. Prior medical condition

Apportionment does not just come from prior injuries. An employer takes an injured worker as they find them. Anyone who starts a job may have a chronic medical condition such as arthritis or diabetes.

Example: Jonah is a construction worker and files a claim for an injury to both knees. The med-legal doctor finds that 25% of Jonah's knee problems are related to arthritis, which is unrelated to work.

Jonah is overweight but when he was younger, he was a long-distance runner. The doctor believes both factors contribute to Jonah's arthritis.

1.4. Importance of medical evidence

Medical evidence is an important factor in determining apportionment. The ability to compare medical records from different time periods can show changes in a specific medical condition.

Comparing diagnostic tests like MRIs over time can help determine apportionment.

Example: Julie injures her neck at work. Julie tells her treating physician that she had a neck injury several years ago. At the time of the prior injury, she had an MRI of her neck.

The doctor sends Julie for a new MRI and obtains the report for the old MRI. The doctor compares the two MRIs to see if Julie's neck condition has changed.

Julie has significant findings on her old MRI, but her condition is worse on the new MRI. The doctor apportions 60% of her current neck disability to the old injury.

If the doctor did not have the prior MRI, he or she might not be able to determine apportionment to a prior injury. However, he could still provide apportionment based on Julie's statements about her prior injury.

Prior treatment records are also important. An injured worker that has had treatment for the same part of the body before a work injury may have apportionment.

Example: Sherri injures her hip at work from a fall down the stairs. At her deposition, she tells the insurance company's attorney that she was treated several years ago at Kaiser for hip pain.

Sherri's treating physician reviews the Kaiser records. The records show that Sherri went to Kaiser four times to see a doctor for hip pain. She also had some physical therapy.

When the doctor writes his Permanent and Stationary report, he notes the prior treatment. The doctor feels the treatment was minor and gives 10% apportionment to Sherri's prior hip condition.

carpal tunnel wrist injury pre-existing condition workers' comp california
It is presumed that if an injured worker has a prior workers' compensation award, it still exists if there is a new injury.

2. Apportionment if there is a prior workers' compensation settlement

It is presumed that if an injured worker has a prior workers' compensation award, it still exists if there is a new injury.2 The prior award is treated like a pre-existing condition.

The prior award percentage is subtracted from the new disability percentage.3

Once there is an award, an employee cannot claim he or she has recovered from the prior injury.4 It stays with an employee for the rest of his or her life as long as the current California workers' compensation rules remain.

Example: Justin has a prior Stipulated Award for his shoulder of 14%. He gets a new injury to the same shoulder. After treatment, he is found to have 24% permanent disability for his shoulder.

Since Justin has a prior award of 14%, he had a 14% permanent disability of his shoulder before his current injury. If his current disability of 24% is not reduced, Justin will get paid for the 14% a second time. Therefore the 14% is subtracted from the 24%.

Justin's current claim is only 10% permanent disability.

However, if an injured worker does not have a prior award, there is no value to subtract. A prior award will come from a Stipulated Award or a trial and judicial decision.

In a Compromise and Release, there is no permanent disability percentage award. It is a lump sum payment to close out a workers' compensation case.

Apportionment where there is a prior Compromise and Release is treated as a pre-existing condition. Any apportionment will come from the doctor stating what percentage of the current disability comes from the pre-existing condition.

Example: Justin has a prior shoulder injury settled by Compromise and Release for $28,000. After treatment for a new injury to his shoulder, Justin's med-legal evaluator finds that Justin has 24% permanent disability for his shoulder.

The doctor reviews medical reports and diagnostic tests from Justin's prior injury and determines that 50% of his current disability is from his prior injury.

This brings Justin's permanent disability for his shoulder down to 12% in his current claim.

2.1. Additional limitations on permanent disability

An injured worker cannot have more than 100% permanent disability in each region of the body over a lifetime. The regions of the body are:

  • hearing
  • vision
  • mental and behavioral disorders
  • spine
  • upper extremities, including the shoulders
  • lower extremities, including the hip joints
  • head, face, cardiovascular system, respiratory system, and all other systems or regions of the body not listed5

Example: Jenny has a prior 25% award for her left knee, a prior 19% award for her right hip, and a prior 8% award for her right ankle. Jenny has a new injury to her right knee.

Jenny already has awards totaling 52%. The maximum permanent disability she could obtain for her right knee injury is 48%. At that point, she would have 100% disability for her lower extremities.

3. Pre-existing conditions that are not apportioned

An employee can have a lighting up of a pre-existing condition that will not have any apportionment if it was not disabling.6

An employer hires an employee in his or her current condition. If an employee is more fragile, the employer is still responsible for any injury. It is not a defense to say it would not happen to a stronger employee.7

However, the employer is not responsible for the natural progression of a pre-existing condition.8

Example: Stephen has a heart condition that does not have any symptoms. After working in a stressful sales job for eight months, he has a heart attack.

The doctor that evaluates Stephen finds that if he was not exposed to the stressful situation, his heart condition would not have changed. Therefore, there is no apportionment.

Genetics is not generally considered a factor in apportionment. But a congenital or hereditary condition can be difficult to distinguish from genetics. The issue is still in dispute in California workers' compensation.9

couple looking at medical report california workers' comp
When those injuries have the same permanent and stationary date, they are kept separate to determine the permanent disability and case value.

4. Apportionment between two current injuries

There are situations where an employee has two injuries with the same employer that overlap. When those injuries have the same permanent and stationary date, they are kept separate to determine the permanent disability and case value.

Each injury must be separately compensated.10

Example: Harrison works for an appliance repair company. While on a job, he injures his wrist.

His doctor finds that Harrison has two injuries. He has a specific injury that occurred on the day he injured his wrist. But the condition of his wrist could not have just been caused by an injury on one day. He also has a cumulative trauma. His wrist was injured over time doing repetitive activities.

Harrison has 18% permanent disability for his wrist. But the apportionment is 50% to each injury.

If Harrison had 18% disability his injury would be worth $18,995. The two 9% injuries are worth $7,830 each. Harrison gets $3,335 less because of the apportionment into two injuries.

However, there may be certain times when a doctor cannot separate the injuries and must keep them together.11

Example: Teresa falls at work and injures her back. She files a claim and goes to the doctor to begin treatment. The next week she falls again and injures her back.

After many months of treatment and three epidural injections, Teresa's condition has stabilized. She is found to have 34% permanent disability for her back by her doctor.

The doctor is aware there are two injuries but has no information to calculate apportionment between the two. Therefore the 34% disability will be the final disability.

5. How is apportionment calculated in the permanent disability rating?

Any doctor who issues a report about permanent disability must address the cause of the disability.12 Part of causation is determining apportionment. The doctor must:

  • state that he or she is familiar with apportionment
  • describe the exact nature of the apportionment
  • set forth a basis for an opinion13

The doctor must answer:

  • What percentage of the injury was caused by work?
  • What percentage was caused by other factors before or after the work injury?14

If a doctor cannot make an apportionment determination, he or she should consult another doctor.15

It is an injured worker's responsibility to disclose prior permanent disability or physical impairments if asked.16

A doctor's report is only part of the permanent disability rating. An injured worker's permanent disability comes from:

The PDRS takes the rating found by the doctor and adjusts it up or down based on the injured worker's age and occupation. Injured workers that are older may have a harder time training for new employment, so they will get an adjustment up, while a younger workers rating is adjusted down.

Injuries in certain occupations are more significant. Injuring a knee is more significant if a person is a warehouse worker than if he or she is an office worker. This also affects the rating

Once all the adjustments are made, the apportionment is factored in.

Example: Jim is a 52-year-old welder and injures his lumbar spine at work. The doctor gives him 7% impairment for his lumbar spine and apportions 25% to a pre-existing condition. This means 75% of his permanent disability is related to work.

The final permanent disability rating is:

75% ( – 8% – 11 – 370G – 13 – 16) 12% permanent disability

code for lumbar spine


doctor's rating


result of adjustment to turn medical rating into a work rating


occupation and affect lumbar spine injury has on it


result of adjustment for welder and lumbar spine injury


result of adjustment for age of work

After the permanent disability rating is complete, the apportionment is factored in. Jim's disability is reduced by 4%, which is 25% of 16.

6. Apportionment does not affect future medical care

Even if there is apportionment to a non-work-related condition, there is no apportionment of the medical care. The employer or insurance company must pay for all medical care necessary to treat an injury. The injured worker does not have any co-pays or deductibles.

An injured worker who needs significant medical treatment can obtain it through workers' compensation even though the majority of the injury is not work-related.

Example: Joey has been a smoker for over 20 years. He also works with chemicals. He develops lung cancer. The doctor finds that 80% of Joey's cancer is due to smoking and 20% is due to work.

However, all of Joey's future treatment for his lung cancer must be covered under workers' compensation. Joey will not have to pay for any of the cost of the treatment.

7. What is the importance of apportionment in California workers' compensation?

Apportionment can have a major effect on the value of an injured worker's case.

It is not just apportionment to non-work-related conditions, but also apportionment into two separate injuries that can reduce a case value.

An insurance company that is not able to dispute an injury will spend a significant amount of time looking for apportionment of permanent disability to lower the value of an injured worker's claim.

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For help with filing a workers compensation claim in Calfornia, completing workers comp forms or appealing a denial of benefits, contact us at (855) LAW-FIRM. Our firm helps police officers, firefighters and other workers to get compensation for their job-related injuries in California.

Legal References:

  1. Brodie v. WCAB (2007) 40 Cal. 4th 1313, 1321.

  2. Cal. Lab. Code § 4664(b).

  3. Brodie v. WCAB (2007) 40 Cal. 4th 1313.

  4. Kopping v. WCAB (006) 71 Cal. Comp. Cases 1229.

  5. Cal. Lab. Code § 4664(c).

  6. Sherman v. WCAB 2005 Cal. Wrk. Comp. P.D. LEXIS 37.

  7. Braewood Convalescent Hospital v. Workers' Comp. Appeals Bd., (1983) 34 Cal. 3d 159, 165.

  8. Escobedo v. WCAB (2005) 70 Cal. Comp. Cases 604, 617.

  9. City of Jackson v. Workers' Comp. Appeals Bd., 11 Cal. App. 5th 109, 117.

  10. Benson v. WCAB (2009) 74 Cal. Comp. Cases 113, 123.

  11. Benson, at p. 133.

  12. Cal. Lab. Code § 4663(a).

  13. City of Jackson v. Workers' Comp. Appeals Bd., 11 Cal. App. 5th 109, 119.

  14. Cal. Lab. Code § 4663(b).

  15. Id.

  16. Cal. Lab. Code § 4663(c).

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