The Legislature strengthened the work‑causation requirement in 1993 by adding the current definition of “arising out of” and expressly incorporating the concept of “occupational causation.” See ch. 93‑415, § 2, at 73, Laws of Fla. (creating the modern definition of “arising out of”); id. § 112, at 215 (establishing the January 1, 1994 effective date). Under § 440.02(36), Florida Statutes, the Legislature recognized that “there may be numerous contributing causes leading to an injury or disability,” Orange Cnty. MIS Dep’t v. Hak, 710 So. 2d 998, 999 (Fla. 1st DCA 1998), and clarified that when multiple causes exist, the work performed in the course and scope of employment must be the major contributing cause of the injury for the accident to be compensable. § 440.02(36), Fla. Stat.

Flowing naturally from this framework is the long‑recognized principle of workers’ compensation law that an idiopathic condition does not “arise out of” employment unless the employment itself contributes to the risk of the accident or aggravates the resulting injury. S. Bell Tel. & Tel. Co. v. McCook, 355 So. 2d 1166, 1168 (Fla. 1977). This rule reflects the core causation requirement: a purely personal condition cannot defeat compensability unless the workplace adds no hazard and plays no causal role in the accident. This rule reflects the core causation requirement: a purely personal condition cannot defeat compensability unless the workplace adds no hazard and plays no causal role in the accident.

Examples of idiopathic conditions (i.e., personal conditions) that may defeat compensability for fall‑related injuries include purely personal medical events such as fainting or syncope, cardiac arrhythmia, vertigo, leg failure from preexisting condition—conditions that spontaneous falls without any contributing workplace hazard. In these scenarios, there is no exertion in furtherance of the employee’s work.

In contrast are the classic “direct‑impact” accidents—events in which an external mishap or malfunction in the workplace immediately injures the employee. These accidents arise from a discrete hazard inherent in the work environment, such as a hand caught in a press, a machine explosion, a workplace fire, a collapsing ceiling, or even a puncture wound from employer‑provided equipment like a stapler. In these situations, causation is straightforward because there is virtually no room for intervening, non‑work‑related risks. The employee is performing assigned work while exposed to an employer‑created hazard, and that hazard directly and immediately impacts the employee’s body, producing injury. The causal link between the employment and the injury is therefore direct and unmistakable, and any exertion associated with performing the job is sufficient to satisfy the “arising out of” requirement. See Sentry Ins. Co. v. Hamlin, 69 So. 3d 1065, 1070 (Fla. 1st DCA 2011) (noting that injuries caused entirely by “risks peculiar to employment are universally compensable”).

Thankfully, not all compensable accidents must meet these straightforward “direct‑impact” events. Florida law recognizes that many workplace injuries arise from more nuanced circumstances, and compensability does not depend on the presence of an obvious, dramatic external impact. In fact, “[W]here an unexplained fall happens while Claimant is `actively engaged’ in the duties of employment, and where there is no other established basis for the fall, the causal relationship between the employment and the accident is met.”). See Ross v. Charlotte Cnty. Pub. Sch., 100 So.3d 781, 782 (Fla. 1st DCA 2012). Moreover, when no preexisting condition contributes to the accident or injury, and the claimant is engaged in work activity at the time of the event, the claimant has satisfied the requirement of occupational causation. In that circumstance, the workplace activity itself supplies the necessary causal link, and the accident “arises out of” the employment as a matter of law. See Ross, 100 So.3d at 782.

For example, consider a workplace fall that occurs while an employee is walking in furtherance of his employment. Assume that the only evidentiary-supported links in the chain of causation are work-related: the employee is walking at work and for work—e.g., moving between offices or work stations, entering the workplace, or leaving it—when he trips over his own feet and falls. There is no evidence of a pre-existing condition or idiopathic manifestation—such as epilepsy, dizziness, syncope, or a ruptured Achilles tendon—that could have contributed to the fall. Thus, there is no non-work-related link in the causal chain to be weighed against the employee’s work activity as a competing cause.

In these circumstances, the ordinary exertion of walking in the course and scope of employment is sufficient to establish a work-related cause. The “any exertion” test does not inquire into the quality, intensity, or quantity of the exertion. Rather, “any exertion” means precisely that: any effort undertaken in furtherance of the employee’s work is sufficient. Cf. Caputo v. ABC Fine Wine & Spirits, 93 So. 3d 1099 (Fla. 1st DCA 2012) (holding that, in the absence of proof of a pre-existing condition or other competing cause, evidence that the employee was working at the time of his fall was sufficient to satisfy the statutory MCC requirement); Walker v. Broadview Assisted Living, 95 So. 3d 942, 943 (Fla. 1st DCA 2012) (holding that where it was undisputed that the employee was engaged in a work-related activity, such as walking, and there were no competing causes of the accident or injury, the “work activity was de facto the major cause”).

Accordingly, where the evidence establishes that the employee was engaged in work-related activity at the time of the accident, and the record contains no evidence of an idiopathic condition or other non-work-related competing cause, the work activity necessarily constitutes the preponderant cause. “Work here necessarily is the preponderant cause because it is the only cause. There is no relative risk (work versus non-work) to be assessed.” See Silberberg v. Palm Beach County School Board, 335 So.3d 148, 159 (Fla. 1st DCA 2022).

Now add an idiopathic condition to the causation chain. Assume, for example, that the employee fell because his knee gave way while he was walking between offices at work. The “any exertion” test no longer resolves the causation inquiry because the evidence establishes more than one potential cause of the accident: the employee’s work-related activity and a personal, idiopathic risk. The work activity—walking between offices—therefore is no longer the identified cause of the accident; it is merely a potential cause, and it may be no more than an incidental one.

The fact that the employee was walking for work does not, standing alone, establish that the work activity contributed to the accident in any meaningful sense. The knee might have given way while the employee was walking anywhere, at any time, for any purpose. Thus, once an idiopathic condition enters the causal chain, the inquiry must shift from whether the employee engaged in any work-related exertion to whether the work environment or work activity exposed the employee to a hazard or exertion beyond that encountered in ordinary non-work life.

That is the function of the “increased hazard” test. The test identifies, among the competing causes of the fall, whether the work-related activity was the preponderant cause—the cause that contributed sufficiently to the accident to trigger the subsequent links in the causal chain—or whether the employee merely happened to experience an idiopathic event while engaged in an activity that happened to be work-related. In other words, the question is not simply whether the employee was walking for work, but whether the particular walking constituted an increased hazard attributable to the employment: movement that, qua work, exposed the employee to a risk materially greater than the ordinary risk of daily life. See Silberberg, 335 So.3d at 159.

In Leon County School Board v. Grimes, 548 So. 2d 205 (Fla. 1989), the Florida Supreme Court reviewed the First District’s decision in Grimes v. Leon County School Board, 518 So. 2d 327 (Fla. 1st DCA 1987), on the following certified question:

“In applying the pertinent provisions of chapter 440 [Florida Statutes (1985)], are accidents suffered by employees in falls which are attributable to idiopathic causes personal to the employee and result in injuries from collision with the floor, equipment or other conditions of the workplace, permissibly treated as arising out of the employment irrespective of any showing of increased risk or hazard attributable to the work place?“

The Supreme Court framed the issue succinctly: “The central issue in this case concerns injuries which occur at the place of employment but are the result of a condition personal to the claimant and are not caused by the place of employment.”

The pertinent facts: Thelma Grimes was employed by the Leon County School Board as a media technician. The School Board was aware that she had contracted polio as a child and, as a result, wore a full‑length brace on her right leg. The brace contained a manual lock that she was required to fasten each time she stood.

On the date of the accident, Grimes rose from her desk to retrieve a file and locked the brace in the usual manner. As she stood, however, the brace failed, causing her to fall and fracture her left ankle. Her left leg became trapped beneath her as she landed on the carpeted floor. It is this ankle injury for which she sought workers’ compensation benefits. Evidence was also presented that the brace had given way on at least one prior occasion while she was at home.

The Court began its analysis by citing the foundational rule from Foxworth v. Florida Industrial Commission, 86 So. 2d 147, 151 (Fla. 1955): “[I]njuries which arise out of risks or conditions personal to the claimant do not arise out of the employment unless the employment contributes to the risk or aggravates the injury.” It emphasized that Chapter 440 “was not designed to take the place of general health and accident insurance” (General Properties Co. v. Greening, 18 So. 2d 908, 911 (Fla. 1944)), listing key precedents where Foxworth barred recovery for idiopathic conditions:

• Southern Bell Tel. & Tel. Co. v. McCook, 355 So. 2d 1166 (Fla. 1977) (denying benefits where a back injury occurred while bending for toilet tissue due to an underlying idiopathic condition).
• Honeywell, Inc. v. Scully, 289 So. 2d 393 (Fla. 1974) (denying benefits for a fall caused by a fainting spell because workplace hazards did not aggravate the injury).
• Southern Convalescent Home v. Wilson, 285 So. 2d 404 (Fla. 1973) (denying recovery for injuries resulting from an epileptic seizure at work).
• Federal Electric Corp. v. Best, 274 So. 2d 886 (Fla. 1973) (denying benefits following a fatal skull fracture caused by an idiopathic epileptic seizure).

Citing Foxworth, the Grimes Court emphasized that “[w]here the idiopathic fall occurring on the job is merely onto a level floor, compensation for effects of the fall is extremely difficult to justify . . . .” The Court contrasted this with Protectu Awning Shutter Co. v. Cline, 154 Fla. 30, 16 So. 2d 342 (1944), where recovery was allowed after an employee suffered a heart attack and fractured his skull on a concrete floor. In Cline, the extreme hardness of the floor was deemed an increased employment hazard—though the Grimes Court noted that Cline represents the absolute outer limits of the doctrine.

We currently represent a worker who suffered catastrophic injuries after stepping onto a truck’s lift gate, which flexed unexpectedly and caused him to lose his balance. The workers’ compensation insurance carrier denied compensability by raising an idiopathic defense—pointing to a prior surgical leg repair from years earlier (the result of breaking up a fight) and claiming that his preexisting leg condition, rather than the movement of the lift gate, caused the fall.

While our client denies that his idiopathic condition contributed to causing the fall, we are nevertheless confident of passing the “increased hazard” test by showing that the work-related activity was the proponderant cause of the fall.

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Jeffrey P. Gale, P.A. is a South Florida based law firm committed to the judicial system and to representing and obtaining justice for individuals – the poor, the injured, the forgotten, the voiceless, the defenseless and the damned, and to protecting the rights of such people from corporate and government oppression. We do not represent government, corporations or large business interests.

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