Rapid growth in cumulative trauma claims in California is intensifying a long-running dispute over how quickly insurers and employers reject the claims, and whether those early denials are pushing more injured workers toward litigation.

Cumulative trauma claims, which allege that repetitive workplace activity caused an injury over time rather than from a single accident, are now the primary driver of the state’s rising claim frequency and are adding to medical-legal costs and litigation expenses across the system, experts say.

The trend is emerging as insurer results in California deteriorate, according to the Workers Compensation Insurance Rating Bureau of California. The projected accident-year combined loss and expense ratio rose to 127% in 2025 from 124% in 2024, marking the second consecutive year above 120%. Written premium remained stable at about $15.6 billion, and the average charged rate fell to $1.56 per $100 of payroll, its lowest level in more than 50 years, said Tony Milano, Oakland, California-based WCIRB executive vice president and chief actuary, who presented findings during the bureau’s annual conference July 16.

The California Department of Insurance approved a 6.6% average advisory pure premium rate increase effective Sept. 1, 2026, following an 8.7% average increase effective Sept. 1, 2025. Even after both increases, advisory pure premium rates remain 46% below their 2014-2015 high.

The debate over denials surfaced publicly at the WCIRB’s annual conference, where Adam Dombchik, Los Angeles-based managing partner of applicant firm Gordon, Edelstein, Krepack, Grant, Felton and Goldstein, argued that nearly all cumulative trauma claims are often denied within 14 to 21 days and without a proper investigation. He urged employers to accept more obvious claims early, such as those involving longtime employees with clear physical wear, rather than forcing cases into what he called a months-long medical-legal ordeal, according to reporting by WorkCompCentral, a sister publication of Business Insurance. Mr. Dombchik did not respond to Business Insurance’s request for comments.

Scotty Benton, Chino Hills, California-based vice president of workers compensation practice for Sedgwick, pushed back on the idea that denial is “automatic.” Each claim is evaluated on its own merits, and any early denial is issued for a documented reason tied to an active investigation, he said.

The bigger driver of delay is the medical-legal system itself, where insurers frequently cannot secure a qualified medical evaluation within the 90 days allowed to make a decision, or 75 days for first responders, leaving many claims in a state of “conditional denial” while the report is pending, Mr. Benton said. More than 80% of cumulative trauma claims involve attorney representation, with nearly all claims filed after a worker’s employment ends resulting in litigation, he estimated.

The pattern of early denials largely reflects how little employers know when a claim first surfaces, said Jeff Adelson, a partner and general counsel at Irvine, California-based law firm Bober, Peterson & Koby.

Unlike a fall or a machinery accident, a cumulative trauma claim typically becomes known to an employer when an application for adjudication or a claim form is filed, often the first indication that a worker believes years of repetitive tasks caused an injury, he said. With 90 days to accept or deny, employers frequently deny because they lack basic facts: whether the worker ever reported pain to a supervisor, missed time from work, or mentioned symptoms to a doctor, he said.

Mr. Adelson emphasized that an initial denial is not necessarily final. Depositions and discovery, including employment records and job descriptions, can prompt insurers to accept a claim later if the evidence supports it. “Medical evidence” ultimately drives most outcomes, he said.

The dynamic isn’t new, said Sure Log, of counsel with El Segundo, California-based workers compensation defense firm Michael Sullivan & Associates. California’s statutory “low bar” for compensability — employment need only be a “contributing cause” of a condition — makes cumulative trauma claims comparatively easy to plead, especially for long-tenured workers, he said.

The state’s 90-day rule is a major reason why insurers sometimes deny outright: If an employer doesn’t accept or deny within that window, the claim is presumed compensable, and that presumption is hard to rebut, he said.

He also pointed to California’s post-termination defense under the labor code, which typically bars claims filed after a layoff or termination, except when the “date of injury” falls after that date. Many cumulative trauma claims fall under that exception because workers often don’t realize their condition is work-related until after leaving the job. That is why many employers deny cumulative trauma claims filed post-termination, he said.

The financial stakes underline why the dispute matters.

The WCIRB reports that medical-legal service use tied to cumulative trauma claims rose 38% from 2020 to 2024, compared with 2% for other claims, while allocated loss adjustment expenses climbed to $13,860 per indemnity claim in 2025 after roughly 9% annual growth since 2021. About a quarter of cumulative trauma claims carry no medical payment in the first 18 months, and 22% remain open after five years.

Mr. Benton said addressing the trend will likely require broader system reforms rather than claim-by-claim fixes, and that employers should expect cumulative trauma claims to continue to pressure costs over the next three to five years.

Workforce, population and tenure changes fail to account for broad rise in California claims

California’s surge in cumulative trauma claims cannot be fully explained by workforce growth, population changes or changing worker-tenure patterns, according to a California Workers’ Compensation Institute report, which found claims increased even in regions with flat or declining employment.

The report, released Aug. 3, found that cumulative trauma claims accounted for 16.5% of all California workers compensation claims in 2025, up from 9.1% in 2018, with most of the increase occurring after 2021. Researchers found the growth in claims was widespread across every region, industry, body-part category and worker-tenure group examined.

The increase primarily reflected more workers filing cumulative trauma claims rather than a major increase in multiple filings by individual workers, the report said. In a subsample representing 91% of the study claims, about 87% of the increase was attributable to growth in the number of workers filing at least one cumulative trauma claim, while 13% reflected an increase in the average number of claims filed per worker.

The report also identified a significant shift in applicant attorney activity. Southern California law firms represented 79% of cumulative trauma cases involving Northern California employers in 2025, up from 23% in 2019, while the share of those cases filed in Southern California venues rose from 15% to 38%.

Researchers said the trend coincided with the expansion of remote hearings during the COVID-19 pandemic, which reduced geographic barriers to representation for workers. They emphasized, however, that the study did not determine whether the expansion of Southern California attorneys’ activity contributed to the increase in cumulative trauma claims.

Regionally, Los Angeles continued to have the state’s highest cumulative trauma claim rate, at 22.9% in 2025, while the Inland Empire/Orange County region posted the largest increase, rising 10 percentage points to 19.8%. The Valleys recorded the biggest increase in claim volume, rising 136% from 2018 levels, indicating the growth extended beyond areas that historically generated large numbers of cumulative trauma claims.