Workers’ Comp Attorneys Blog

Pre-Existing Conditions Don’t Always Bar a California Workers’ Comp Claim

Many California employees hesitate to file a workers’ compensation claim because they already have an old injury or chronic health condition. They assume their employer or insurance carrier will deny benefits, arguing that the problem existed before the job injury occurred. But under California law, that’s not how the system works.

The state’s workers’ compensation laws recognize that real life isn’t always cleanly divided into “old” and “new” injuries. A work incident that aggravates, accelerates, or lights up a pre-existing condition is still considered compensable. What matters most is whether employment contributed to the need for treatment or disability — not whether the worker was perfectly healthy before the accident.

In this article, the experienced Southern California workers’ comp attorneys at Cantrell Green explain how apportionment works, why pre-existing conditions do not automatically bar recovery, and what kind of medical evidence helps establish a valid claim.

Understanding Apportionment in Workers’ Comp Cases

Apportionment is the process used to determine what percentage of an employee’s permanent disability is caused by work versus non-work factors. It’s governed primarily by California Labor Code Sections 4663 and 4664.

In simple terms, apportionment doesn’t eliminate benefits — it divides them. If a worker’s permanent disability is found to be partly caused by pre-existing factors, only the work-related portion is compensable. For example, if a back injury is deemed 70% work-related and 30% due to prior degeneration, benefits are paid on the 70% portion.

Medical evaluators — typically Qualified Medical Evaluators (QMEs) or Agreed Medical Evaluators (AMEs) — provide opinions on apportionment. Their role is to identify and explain any pre-existing conditions and determine how much, if at all, those contributed to the current disability.

The experienced Southern California workers’ comp attorneys at Cantrell Green emphasize that even when apportionment applies, workers still receive substantial benefits for the portion caused or aggravated by their employment.

When a Pre-Existing Condition Becomes a Work Injury

California law draws a clear distinction between a pre-existing condition and a work-aggravated condition. A dormant or asymptomatic condition that becomes disabling because of work activity is considered a new, compensable injury. This is sometimes called the “lighting up” doctrine.

For instance, an employee with mild degenerative arthritis in the knees who begins working on hard concrete floors may develop severe pain and swelling requiring surgery. Even though arthritis existed before employment, the job aggravated it to a disabling level. In such cases, the injury is considered industrial.

California courts have upheld this principle repeatedly. In Ferguson v. Industrial Acc. Comm’n (1958), the court held that an employee’s pre-existing back condition became a compensable industrial injury when aggravated by heavy lifting at work. The key question is always whether job duties contributed — even partially — to the current disability or need for treatment.

The experienced Southern California workers’ comp attorneys at Cantrell Green use this principle to help employees demonstrate how workplace activities worsened or accelerated their pre-existing medical conditions.

Evidence That Supports a Workers’ Comp Claim

Medical documentation is central to proving that employment contributed to the injury. Evaluating physicians must explain, “within reasonable medical probability,” whether workplace exposure, strain, or trauma aggravated a pre-existing problem.

• Important evidence can include:
• Diagnostic tests showing measurable worsening of a condition after work exposure;
• Physician reports comparing pre-injury and post-injury medical status;
• Witness statements or incident reports describing increased pain after specific work activity; and
• Consistent medical history provided to evaluators.

Even in apportionment cases, benefits may include medical treatment, temporary disability payments during recovery, and permanent disability compensation for the work-related percentage.

The experienced Southern California workers’ comp attorneys at Cantrell Green review medical evidence carefully, ensuring that evaluators understand the difference between pre-existing susceptibility and actual disability caused by work. Their experience often prevents insurance carriers from unfairly attributing too much of the injury to prior conditions.

Common Misconceptions About Pre-Existing Conditions

A few widespread myths discourage employees from filing legitimate claims. One is the belief that if you’ve ever had treatment for the same body part, your claim will be denied. In reality, prior medical care does not disqualify a case — it merely informs the apportionment analysis.

Another misconception is that cumulative trauma injuries, such as repetitive stress or gradual wear-and-tear, are automatically considered pre-existing. Under California Labor Code Section 3208.1, cumulative trauma is a valid category of industrial injury when repetitive work activities over time cause or aggravate a condition.

A third myth is that older workers cannot claim benefits because their conditions are “age-related.” Age may influence apportionment percentages, but it does not bar compensability when work contributes to the disability.

The experienced Southern California workers’ comp attorneys at Cantrell Green frequently correct these misunderstandings and advocate for fair evaluation of claims based on medical fact, not assumption.

How Workers’ Comp Attorneys Build a Strong Case

Establishing work contribution often requires coordination between legal and medical experts. Attorneys gather medical records, employment documentation, and witness statements to help evaluators see the full picture. They may also challenge medical opinions that rely on speculation or incomplete evidence.

When apportionment appears excessive or unjustified, an attorney can request supplemental reports, cross-examine evaluators at deposition, or present additional evidence before the Workers’ Compensation Appeals Board (WCAB).

The experienced Southern California workers’ comp attorneys at Cantrell Green have decades of experience managing these complex issues. They understand how to present persuasive medical-legal arguments and ensure injured employees receive the full benefits allowed by law, even when pre-existing conditions are involved.

Why Having Legal Representation Matters

Insurance carriers often use pre-existing conditions as a defense to minimize payouts. They may cite old medical records or prior claims to argue that disability existed before employment. Without skilled representation, employees can lose rightful compensation simply because they lack expert rebuttal.

An attorney familiar with California’s apportionment laws can counter these tactics effectively. By presenting clear, evidence-based medical opinions and legal arguments, workers’ compensation lawyers can ensure that only legitimate non-industrial factors are subtracted from the award.

The experienced Southern California workers’ comp attorneys at Cantrell Green protect clients from these unfair denials and work tirelessly to secure full compensation for every injury or aggravation that occurred on the job.

Top Workers’ Comp Attorneys | Southern California

A pre-existing medical condition does not automatically disqualify an employee from receiving workers’ compensation in California. If your job aggravated, accelerated, or worsened an existing condition, you may still be entitled to benefits. The experienced Southern California workers’ comp attorneys at Cantrell Green understand how to navigate apportionment law, present effective medical evidence, and challenge unfair denials.

If you’ve been told your claim is invalid because of a prior condition, don’t give up your rights. Schedule an appointment with Cantrell Green to discuss your case and learn how California law protects employees with pre-existing conditions who suffer legitimate work-related aggravations.

Top Southern California Workers Comp Attorneys: 800-964-8047