Category: Daily News

This court challenge concerns California’s FAIR Plan, the state-mandated “insurer of last resort” for property owners who cannot obtain coverage in the ordinary market (Ins. Code, § 10090 et seq.). The Plan is an involuntary association of all property insurers licensed in California; each member shares proportionally in the Plan’s writings, profits, and losses based on its market share two years earlier (Ins. Code, § 10095(c)). When the Plan runs short, it may levy an assessment on its member insurers, subject to the Commissioner’s approval.

At issue were two bulletins issued by Insurance Commissioner Ricardo Lara. Bulletin 2024-8 (Sept. 3, 2024) set out a procedure by which FAIR Plan member insurers could seek the Commissioner’s prior approval, under Proposition 103, to recoup any FAIR Plan assessment from their own policyholders. Bulletin 2025-4 (Feb. 11, 2025) updated that guidance after the “highly unlikely event” actually occurred: following the January 2025 Los Angeles wildfires, the FAIR Plan sought approval for roughly $1 billion in assessments — the first in over 30 years — and insurers were permitted to pass through some, but not all, of those costs to policyholders over no more than two years. Per the Department, the median homeowner fee was about $28 per year.

In April 2025, Consumer Watchdog — a nonprofit public-interest organization — sued Commissioner Lara and the Department of Insurance to invalidate the bulletins. Its verified petition raised three claims: that the bulletins were “regulations” adopted without complying with the Administrative Procedure Act; that they exceeded the Commissioner’s authority under the FAIR Plan statutes; and that, by letting insurers pass assessments through to policyholders, they violated the equal profit-and-loss-sharing command of section 10095(c).

This was a trial-court ruling on a petition for a traditional writ of mandate (Code Civ. Proc., § 1085), not an appeal. Earlier, in a July 22, 2025 order, the court had sustained the Department’s demurrer without leave to amend as to the first two causes of action — holding that the bulletins fell within an APA exception and that the Commissioner had authority for the pass-throughs under Proposition 103. Only the third cause of action — the claim that the bulletins violate section 10095(c) — survived to be decided on the merits. Consumer Watchdog argued that section 10095(c) reflects a legislative design of “symmetry,” under which member insurers who reap the Plan’s profits must also absorb its losses, and that shifting assessment costs to non-FAIR-Plan policyholders effectively turns ordinary consumers into reinsurers of their own insurers.

The trial court denied the petition in its entirety, along with the requests for declaratory and injunctive relief. The court declined to reach the Department’s argument that Consumer Watchdog lacked standing, resolving the case instead on the merits.

The court first set aside the bulk of Consumer Watchdog’s briefing, which re-argued that the bulletins were not authorized under Proposition 103. That question, the court held, had already been decided at the demurrer stage — where it ruled the Commissioner had Proposition 103 authority for the pass-throughs — and the time to seek reconsideration had passed. Attempts to reframe the argument as newly raised questions were unavailing.

On the sole surviving claim, the court held the statute’s meaning is plain: it governs how writings, profits, losses, and expenses are allocated among FAIR Plan member insurers — the Plan’s internal affairs — and says nothing about what an insurer may later do with its own policyholders. The court found Ohio Casualty Ins. Co. v. Garamendi (2006) 137 Cal.App.4th 64, on which Consumer Watchdog relied, addressed only insurers’ ongoing loss-sharing obligations to one another, not their relationships with policyholders. As the court put it, nothing in the statutory text conditions an insurer’s proportional share of Plan expenses on ultimately absorbing those costs rather than merely paying them initially; the statute regulates the apportionment obligation itself, not the insurer’s later financial decisions.

Because the statute was unambiguous, the court refused to resort to canons of construction or to compare the FAIR Plan against other insurance “safety-net” programs (CIGA, CLHIGA, and the CEA) that expressly authorize pass-throughs. It distinguished each of Consumer Watchdog’s authorities — In re Jennings (2004) 34 Cal.4th 254, BullsEye Telecom, Inc. v. Public Utilities Com. (2021) 66 Cal.App.5th 301, Goldstein v. California Unemployment Ins. Appeals Bd. (2019) 34 Cal.App.5th 1006, and Medical Bd. of California v. Superior Court (2001) 88 Cal.App.4th 1001 — noting that each involved a genuinely ambiguous statute and that none endorsed reading an affirmative limitation into a statute from a comparison to different schemes. Invoking the plain-meaning rule (Kavanaugh v. West Sonoma County Union High School Dist. (2003) 29 Cal.4th 911; Burden v. Snowden (1992) 2 Cal.4th 556), and finding Gomes v. Mendocino City Community Services Dist. (2019) 35 Cal.App.5th 249 more persuasive, the court concluded that the absence of express pass-through language in the FAIR Plan statutes could not be construed as an affirmative limit on authority the Commissioner otherwise holds under Proposition 103.

The two sides framed the outcome very differently. In a July 1, 2026 press release titled “Commissioner Lara defeats attempt to undermine California insurance market,” the Department cast the ruling as vindication of the Commissioner’s authority to stabilize the market.  (The Department’s framing was echoed in trade coverage.)

Consumer Watchdog, in a same-day statement (“Court Upholds FAIR Plan Surcharges, Consumer Watchdog Weighs Appeal”), respectfully acknowledged the ruling but sharply criticized the Commissioner and said it is reviewing its options, including an appeal.

The litigation sits within a broader, contentious backdrop around the commissioners “Sustainable Insurance Strategy.” Consumer Watchdog has repeatedly tied the case to criticism of the Commissioner, and has noted that former Insurance Commissioner (and later Congressman) John Garamendi publicly urged Lara to resign in 2025, saying he had not been willing to stand up to the insurance industry. Whether Consumer Watchdog appeals — which would move the section 10095(c) question, and potentially the reserved standing and Proposition 103 issues, before the Court of Appeal — remains to be seen.

A new dispute grew out of Vaughn v. Tesla, Inc. (Alameda County Super. Ct. No. RG17882082), a 2017 class action alleging that Black employees suffered racial discrimination and harassment — including regular use of racial slurs by coworkers and supervisors — at Tesla’s production factory, in violation of the Fair Employment and Housing Act (Gov. Code, § 12940, subd. (a)). The complaint alleged Tesla maintained a policy of tolerating a hostile work environment and a pattern or practice of ignoring and inadequately investigating harassment complaints.

In Vaughn, the trial court granted class certification only in part — certifying three common “pattern or practice” liability issues but declining to certify a class for individual liability or damages, and ordering that each worker seeking damages file a separate lawsuit. The court later denied leave to add 531 class members as individual plaintiffs, and ultimately decertified the class after the plaintiffs conceded they could not produce the 200 class-member witnesses their stipulated trial plan required.

Acting on the court’s own instruction to sue separately, 440 former Vaughn class members filed five complaints in mid-2025, each joining between 54 and 98 individual plaintiffs. All alleged FEHA claims for racial discrimination, harassment, and failure to prevent — asserting they worked at the same Tesla factory, were subjected to similar race-based mistreatment, and were harmed by Tesla’s common practice of failing to systematically address racist conduct.

Weeks after the complaints were filed — and before Tesla filed any demurrer — the trial court issued its own order to show cause why it should not find “inappropriate joinder.” After argument, the court found misjoinder and ordered that in each of the five cases “all Plaintiffs except for the first name on the complaint must be dismissed” and must refile as single-plaintiff complaints. The court reasoned that different workers experienced different harassment in different locations at different times, that there was “virtually no scenario” for a common trial with over 50 plaintiffs, and that its experience in complex litigation let it anticipate the problems these complaints would cause. It also cited concerns about discovery burdens and the loss of filing fees. The plaintiffs sought writ relief; the Court of Appeal stayed proceedings, consolidated the five petitions, and issued an order to show cause.

The Court of Appeal granted the petitions and directed issuance of a peremptory writ of mandate ordering the trial court to vacate its misjoinder order and allow the five original complaints to proceed in the published case of Smith et al. v. Superior Court (Tesla, Inc., Real Party in Interest) – Case No. A174789 (June, 2026). The court took up the matter by writ because the issues were likely to recur and presented legal questions of significant importance.

Because the court dismissed at the pleading stage before discovery (and conceded its OSC was “in essence a demurrer based on misjoinder”), the Court of Appeal reviewed the ruling de novo, assuming the truth of the complaints’ allegations and drawing all reasonable inferences in favor of joinder. Whether misjoinder was proper was a question of law, not a matter of discretion.

The permissive-joinder statute (Code Civ. Proc., § 378) lets plaintiffs join if their relief arises from the same transaction or series of transactions and shares a common question of law or fact. Joinder statutes are liberally construed, and a right to relief arises from the same transaction so long as there is “any factual relationship between the claims” (Petersen v. Bank of America Corp. (2014) 232 Cal.App.4th 238). Applying that breadth, the court relied on Anaya v. Superior Court (1984) 160 Cal.App.3d 228 (200-plus employees exposed to chemicals at one facility over decades were properly joined) and Petersen (965 borrowers harmed by one lender’s common deceptive scheme were properly joined based on commonality of liability, despite widely varying damages). Here, the plaintiffs alleged a single company-wide policy or practice of ignoring racist conduct at one factory — enough to satisfy section 378. That the harassment occurred at different times and places did not defeat joinder; “the salient point is that liability is amenable to mass action treatment.”

The court found Moe supportive: just as an employer’s negligent hiring and supervision was a “series of transactions” exposing multiple assault victims to harm, Tesla was the common entity alleged to have let known harassment persist. It distinguished the cases Tesla cited — David v. Medtronic, Inc. (2015) 237 Cal.App.4th 734 (a medical device with no single scheme; different surgeries, surgeons, and representations), Aghaji v. Bank of America, N.A. (2016) 247 Cal.App.4th 1110 (mortgage plaintiffs with no overarching plan), and Coleman v. Twin Coast Newspaper, Inc. (1959) 175 Cal.App.2d 650 (separate trespasses on separate premises) — as all lacking the common-policy allegation present here. It held the Vaughn decertification did not bind these individually represented plaintiffs (that ruling turned on a witness-production failure, and the court there expressly disclaimed any suggestion that a pattern-or-practice trial is inherently unmanageable), and that federal Rule 20 cases were inapposite given both their lack of a common-policy allegation and the more demanding federal pleading standard.

Section 379.5 does not authorize dismissal. The court rejected the argument that section 379.5’s case-management authority let the court order single-plaintiff filings. Section 378 commits the joinder decision to the plaintiffs, not the judge; section 379.5 lets a court sever trials or make just orders after parties are joined, but not undo a proper joinder. Drawing on Estrada v. Royalty Carpet Mills, Inc. (2024) 15 Cal.5th 582, the court reasoned that trial courts lack inherent authority to strike claims on manageability grounds, and that broad “interests of justice” language (there, § 128; here, § 379.5) does not supply it. That the Legislature authorized dismissal for misjoinder by demurrer (§ 430.10, subd. (d)) but included no such power in section 379.5 — and enacted a counterpart to federal Rule 20 but not to Rule 21 (which allows dropping parties) — confirmed the omission was deliberate. Filing fees, too, are set by the Legislature (Gov. Code, §§ 70611, 70616), not the court, and section 379.5 protects parties from undue expense, not the court itself.

The court acknowledged the trial court’s “formidable” challenge managing 440 plaintiffs and pointed to legitimate tools — separate trials by party or claim (§§ 379.5, 1048), tracking spreadsheets, and the case-management measures endorsed in Estrada and Petersen. But any broader limits on permissive joinder, it held, must come from the Legislature. It also found the recent decision in J.O. v. Superior Court (2026) 19 Cal.5th 753 inapposite, concluding the situation came nowhere near an unconstitutional interference with a core judicial function.

In 2020, attorneys Jennifer McGrath and Darren Kavinoky formed McGrath Kavinoky LLP for a single purpose: to represent victims of sexual abuse by Dr. James Heaps, a gynecologist at UCLA. Jane Doe 1 retained the firm in January 2020, at which point it already represented at least 36 former Heaps patients. Jane Doe 2 retained the firm in February 2021; five weeks later the firm told her it represented 180 patients. The firm ultimately represented 312 clients in separate but coordinated cases against Dr. Heaps and UCLA.

In January 2022, the firm told Does 1 and 2 it had tentatively reached an aggregate settlement. Both agreed. The court appointed retired judges to allocate the $374.4 million global settlement; Doe 1 received $1.4 million and Doe 2 received $1.7 million, less the firm’s contingency fee and costs.

In June 2024, Does 1 and 2 sued the firm and its named partners (collectively, McGrath Kavinoky), asserting professional negligence, breach of fiduciary duty, fraudulent misrepresentation, fraudulent concealment, breach of contract, breach of the implied covenant, and an accounting. They alleged they were among the most severely harmed victims, that the lawyers had promised individualized handling and made specific high-value promises about their cases, that they were “bullied” into the settlement through an improper allocation process — and, critically, that the firm never disclosed, or obtained informed written consent to, the conflicts of interest inherent in representing many clients who would compete for shares of a single settlement.

McGrath Kavinoky moved to compel arbitration under arbitration clauses in its engagement agreements. Does 1 and 2 opposed, arguing the firm violated rule 1.7(b) of the Rules of Professional Conduct — which bars representing a client where there is a significant risk the representation will be materially limited by the lawyer’s duties to another client, absent informed written consent — and that this violation rendered the agreements, including their arbitration clauses, unenforceable.

The trial court denied the motion to compel arbitration. It found that when the plaintiffs signed their retainers, the likelihood of a conflict was high: the firm represented dozens of clients with claims against the same defendant, litigated them in the aggregate toward a global settlement, and so placed each plaintiff in competition with every other for a slice of the recovery. The firm’s failure to disclose that conflict invalidated the retainer agreements and the arbitration clauses within them. McGrath Kavinoky appealed.

The Court of Appeal affirmed the order denying arbitration in the published case of Jane Doe 1 et al. v. McGrath Kavinoky LLP et al. -Case No. B343201 (June 2026). The decision is certified for publication because it resolves a question of first impression in California: whether a lawyer violates rule 1.7(b) — and thereby voids the engagement agreement — by representing multiple clients suing the same defendant for similar injuries without obtaining informed written consent at the outset. The court held that the rule in the 2018 Sheppard, Mullin Supreme Court opinion applies, even though Sheppard involved an actual conflict and this case involves a potential one.

In Sheppard, Mullin, Richter & Hampton, LLP v. J-M Manufacturing Co., Inc. (2018) 6 Cal.5th 59, the Supreme Court held that when a lawyer enters an engagement agreement in violation of an ethical rule, the entire agreement — including its arbitration clause — is unenforceable as against public policy. Citing Civil Code section 1667, the Court reasoned that a contract is unlawful if it is contrary to an express provision or policy of law, and that the Rules of Professional Conduct are not merely guidance for the bar but an expression of public policy protecting the public. Crucially, where grounds exist to void the entire contract, those grounds also vitiate the arbitration clause and prevent severance.

Rule 1.7(b) was violated at the outset. The court held substantial evidence supported the trial court’s finding that a conflict was highly likely when the plaintiffs signed on. Two lawyers who formed a firm specifically to pursue Heaps’s former patients could reasonably be inferred to have intended to represent as many as possible and to resolve them through an aggregate settlement — which is exactly what occurred, only eleven months after Doe 2 signed the retainer agreement. From the start there was a significant risk that clients would disagree about settling, that the defendants might condition any deal on a high participation rate, and that the clients would necessarily compete for their shares — meaning the firm’s ability to advocate for each was materially limited by its duties to the others. Lacking informed written consent, the firm violated rule 1.7(b), which under Sheppard voided the agreements.

The court drew heavily on persuasive authority in an area with no direct California precedent, including ethics opinions and commentary recognizing that conflicts inhere in collective representation. It cited the Bar Association of San Francisco’s Formal Opinion 2017-1 (Sept. 2017), ABA Formal Opinion No. 06-438 (Feb. 10, 2006), and scholarship by Erichson (Beyond the Class Action (2003) 2003 U.Chi. Legal F. 519) and Moore (Ethical Issues in Mass Tort Plaintiffs’ Representation (2013) 81 Fordham L.Rev. 3233), all for the proposition that such conflicts must be disclosed and consented to at the outset of the representation. It also pointed to Bridgepoint Construction Services, Inc. v. Newton (2018) 26 Cal.App.5th 966, where disqualification was proper because multiple clients sought the same damages from a single pool.

The court rejected each of McGrath Kavinoky’s distinctions. It declined to apply Brawerman v. Loeb & Loeb LLP (2022) 81 Cal.App.5th 1106 — where the illegality lay in performance of a retainer by an unlicensed attorney rather than in entering it — because here the violation occurred upon entering the agreements without consent. It rejected the argument that Sheppard reached only actual conflicts, noting rule 1.7 requires informed written consent for both actual (rule 1.7(a)) and potential (rule 1.7(b)) conflicts, and that Sheppard’s rationale applies equally to both. It dismissed the concern that this invites improper “post-hoc” hindsight inquiry, observing that trial courts routinely sit as triers of fact in deciding arbitration motions and are well-equipped to assess whether a significant risk existed at an earlier time. It also clarified that Sheppard expressly left open only the enforceability of blanket advance conflict waivers — an issue not present here, since the firm never claimed to have obtained one.

Arbitration could not be severed. The court held McGrath Kavinoky forfeited its severance argument by not raising it below, and that it failed on the merits regardless: under Sheppard, when an entire contract is void for illegality, the arbitration clause falls with it. The court distinguished the firm’s cited severance and fraud-in-the-inducement cases — including Ericksen, Arbuthnot, McCarthy, Kearney & Walsh, Inc. v. 100 Oak Street (1983) 35 Cal.3d 312 — because those involved either severable provisions in otherwise valid contracts or claims of fraudulent inducement, not a claim that the entire agreement was illegal and void as against public policy.

This en banc decision gathered twenty-four individual cases (some carrying multiple case numbers) that shared a common thread: each involved a Compromise and Release (“C&R”) agreement submitted for approval at the Van Nuys District Office, and each was handled by the same workers’ compensation administrative law judge (“WCJ”), Karinneh Aslanian.

The underlying claims were varied but followed recognizable patterns. Many were cumulative-injury or psychiatric claims premised on a “hostile work environment” – filed by ramp scrubbers, warehouse and delivery workers, nursing assistants, laborers, and others against employers including ABM, Amazon, Lyft, FedEx, and NBC Universal. The proposed settlements ranged from roughly $4,000 to $37,500. A recurring feature was that the parties wished to settle a denied claim quickly – often expressly to “buy their peace” – and frequently without any medical reporting on file, sometimes before any discovery or qualified medical evaluator (“QME”) examination had occurred. In several cases the defendants’ own cover letters acknowledged that no medical reports existed to support an injury.

Importantly, none of these matters had proceeded to an evidentiary hearing on the merits before reaching the Appeals Board.

In each case, rather than approving or formally disapproving the settlement, the WCJ issued an Order Suspending Action (“OSA”) on the C&R. Across the cases, the OSAs went well beyond requesting minor corrections. The WCJ generally:

– –  demanded supporting medical documentation to test adequacy, treating the absence of medical evidence as fatal;
– –  directed applicants, in the text of the OSA, to either obtain a medical evaluation or dismiss the claim with prejudice;
– –  requested witness statements, information about related civil lawsuits, and the source of any benefits paid; and
– –  required applicants’ attorneys to justify the requested 15% attorney’s fee.

The OSAs issued without first giving the parties notice and an opportunity to be heard. In the accompanying Reports to the Board, the WCJ used pointed language – referring to a “free cash money handout system,” asserting that an applicant who would not attend even one medical exam “is clearly not injured,” and describing the Van Nuys venue as a “haven” for a “get rich quick” scheme in which the WCJ “will no longer participate.”

The applicants Petitioned for Removal, arguing the OSAs improperly compelled additional discovery, that the WCJ exceeded the permissible scope of review, and that a WCJ may review only whether a settlement is adequate.

The Appeals Board, sitting en banc by unanimous vote, granted consolidated and granted 24 Petitions for Removal from various Orders Suspending Action, all issued by the same WCJ and issued an en banc decision in the captioned case of Calvin Gaines, et al. v. ABM Aviation, Inc., Adj. Nos. ADJ20216367 et al. (Van Nuys District Office) (June 2026). As its Decision After Removal, the Board rescinded every OSA, disqualified WCJ Aslanian from all twenty-four cases, and returned each matter to the Presiding WCJ for reassignment to a new judge.

Although the Applicants’ Petition was granted, this case was not an affirmance. It a reversal of the WCJ’s orders – though a nuanced one. The Board did not adopt the applicants’ broadest position. It held that a WCJ’s authority to scrutinize settlements is real and substantial: a WCJ may demand relevant medical records, may seek additional information bearing on valuation, and may delay approval until adequacy can be assessed. What the WCJ could not do was use an OSA to compel evaluations, dismissals, or fee reductions without notice, due process, and a record – and could not bring open hostility to the bench.

A workers’ compensation settlement is enforceable only after WCAB approval; in approving it, the WCJ must determine the agreement is valid and adequate to protect the injured worker and the public interest.
Where a settlement’s terms are inconsistent, non-compliant with the Labor Code, or inadequate, the WCJ may investigate through an OSA – and, if the parties do not supply sufficient information, may hold a hearing to create an evidentiary record establishing adequacy.

Due process drove the removal. Settlement review proceeds by stipulation, and there is ordinarily no due-process problem when a WCJ approves a joint request. But once a WCJ intends to reject a settlement or condition its approval, the parties are owed notice and an opportunity to be heard. The OSAs here delivered ultimatums – get evaluated or dismiss with prejudice – without any hearing. Because Appeals Board decisions must rest on an admitted evidentiary record (Hamilton v. Lockheed Corp. (2001) 66 Cal.Comp.Cases 473 (Appeals Board en banc)) and a WCJ cannot enter judgment on the pleadings, the proper path when adequacy is genuinely in doubt is to set a hearing and build a record, not to coerce the parties by order.

The Board emphasized that substantial medical evidence is not required to support a stipulation. Stipulations exist precisely to obviate the need for proof and narrow the issues (County of Sacramento v. Workers’ Comp. Appeals Bd. (Weatherall) (2000) 77 Cal.App.4th 1114 [65 Cal.Comp.Cases 1]). The only requirement is that sufficient information exist in the formal record to support the adequacy finding. The WCJ erred by treating missing medicals as disqualifying and by, in effect, ordering medical evaluations inside an OSA – an order that may issue only after proper notice, and a medical-legal evaluation that may be compelled only after an evidentiary hearing establishes a basis for it.

The Board grounded the WCJ’s review power in the purpose of approval: protecting workers who might accept “unfortunate compromises because of economic pressure or lack of competent advice” (Johnson v. Workmen’s Comp. Appeals Bd. (1970) 2 Cal.3d 964 [35 Cal.Comp.Cases 362], quoting Chavez v. Industrial Acc. Com. (1958) 49 Cal.2d 701 [321 P.2d 449]), and protecting the public interest by ensuring benefits are not improperly shifted onto public programs such as Medicare, Medi-Cal, EDD, and Social Security (Department of Rehabilitation v. Workers’ Comp. Appeals Bd. (2003) 30 Cal.4th 1281 [68 Cal.Comp.Cases 831]). The Board also reaffirmed that the WCAB’s jurisdiction reaches only Labor Code benefits, and mere execution of a preprinted form does not release claims outside workers’ compensation (Camacho v. Target (2018) 24 Cal.App.5th 291 [83 Cal.Comp.Cases 1014]).

Protecting insurers from “overpaying” is not within adequacy review – if anything, evidence that a carrier is overvaluing a claim suggests the settlement is adequate. Inquiry into civil suits is permissible only to the limited extent it bears on a possible third-party credit, and must occur on the record. And while requesting documentation to justify the 15% attorney’s fee was proper (the WCAB is the final arbiter of fee reasonableness under Vierra v. Workers’ Comp. Appeals Bd. (2007) 154 Cal.App.4th 1128 [72 Cal.Comp.Cases 1128]), the remedy for a disputed fee is a hearing – the C&R may be approved with the fee held in trust – not a coercive order.

Finally, under Labor Code section 5311 and Code of Civil Procedure section 641(f)–(g), a WCJ may be disqualified for having formed or expressed an unqualified opinion on the merits or for a state of mind evincing bias. The Board found the WCJ’s “free cash money handout” and “get rich quick scheme” commentary plainly demonstrated both, reminded the WCJ of her obligations under the Code of Judicial Ethics, and ordered reassignment of all twenty-four cases to new judges.

Zimmer Biomet Holdings, Inc. (NYSE: ZBH), headquartered in Warsaw, Indiana, is a global medical technology company with a portfolio focused on maximizing mobility and improving musculoskeletal health. It was named to Forbes’ America’s Best Companies 2026 list and employs approximately 18,000 people worldwide.

According to a new study published in the journal Diagnostics, a machine learning algorithm developed by Zimmer Biomet has demonstrated significantly higher accuracy in diagnosing periprosthetic joint infection – one of the most dreaded and expensive complications in orthopedic surgery – than experienced physicians evaluating the same cases.

Periprosthetic joint infection, or PJI, occurs when bacteria or fungi infect the tissues surrounding an artificial joint after knee or hip replacement surgery. It affects roughly 1 to 2 percent of primary joint replacements – a number that sounds small until you consider that more than one million joint replacements are performed in the United States each year. PJI is the leading cause of failure after total knee replacement and the third leading cause after total hip replacement. In severe cases, it can lead to amputation or death. Five-year mortality rates following PJI of the hip have been reported as high as 25 percent.

The core clinical challenge is diagnosis. PJI is notoriously difficult to identify, particularly in culture-negative cases – where standard laboratory cultures fail to grow an organism – and in borderline cases where symptoms and test results are ambiguous. There is no single gold-standard diagnostic test in the United States. Instead, physicians must synthesize multiple laboratory results, clinical findings, and imaging studies to reach a judgment. Published research has shown that even experienced specialists often struggle with diagnostic consistency, leading to delayed treatment when infection is present or unnecessary revision surgery when it is not.

The new tool, called SynTuition, is a machine learning algorithm that analyzes results from Zimmer Biomet’s Synovasure comprehensive PJI test panel – a battery that measures 11 biomarkers in synovial fluid drawn from the suspect joint. Rather than requiring a physician to manually interpret each biomarker result and weigh them against diagnostic criteria, the algorithm identifies patterns across all 11 markers simultaneously and generates a continuous probability score from 0 to 100, estimating the likelihood that the patient has a periprosthetic joint infection.

The model was built using a dataset of more than 104,000 synovial fluid samples collected from nearly 3,000 institutions between 2018 and 2024 — an enormous training dataset by orthopedic research standards.

In the study, 12 physicians were presented with 274 clinical vignettes representing suspected PJI cases and asked to provide diagnoses. Their results were compared against both an expert-adjudicated clinical reference standard and the SynTuition algorithm’s output.

The results were striking. The AI algorithm achieved 96 percent overall agreement with the expert-adjudicated reference, compared to 90.8 percent for the pooled physician group. More importantly, the algorithm showed dramatically lower diagnostic uncertainty. Physicians frequently expressed indecision – particularly in culture-negative and borderline cases, which are precisely the cases that drive the most disputes in clinical practice. The AI tool provided a definitive probability score in every case, eliminating the ambiguity that leads to diagnostic delays.

The study also conducted a cost analysis. Misdiagnoses – both false positives (leading to unnecessary revision surgery) and false negatives (leading to delayed treatment and progression of infection) – carry significant economic consequences. The researchers found that the AI tool’s superior accuracy translated to meaningful cost reductions compared to standard physician-driven diagnosis.

This study is part of a broader trend in orthopedic medicine: the integration of artificial intelligence into clinical decision-making at critical junctures in patient care. Diagnosing PJI is one of the most consequential decisions an orthopedic surgeon makes – get it right, and the patient receives timely, targeted treatment; get it wrong in either direction, and the clinical and financial consequences are severe.