In this appeal from a decision by the workers’ compensation commissioner denying benefits to the claimant, the parties dispute whether the injury arose out of and in the course of employment. The district court reversed the commissioner’s decision, and the court of appeals reversed the district court. We vacate the decision of the court of appeals, reverse the district court judgment, and remand to the commissioner for further proceedings.
I. Background Facts and Proceedings
Jerry Meyer obtained employment at an IBP plant in Waterloo through a staffing agency called Advance Services, Inc. (ASI). ASI placed Meyer at IBP on October 10, 2000. Meyer was assigned a job that required him to cut the tongues from hog heads delivered on a conveyor belt and to place the tongues on another conveyor belt. This job is known as “popping tongues.” Meyer remained an employee of ASI until he completed a sixty-day probationary period.
Meyer first experienced pain in his hand at work during this probationary period, when he was still employed by ASI. He experienced swelling in his fingers and soreness in his wrist. He notified IBP, visited the health department at IBP, and was told it was '“break-in pain.” Meyer *216 continued working with no restrictions or other actions taken. His employment with ASI concluded on Friday, December 15, 2000.
On Monday, December 18, 2000, IBP hired Meyer as a regular employee to perform the same job he performed during his probationary period. Meyer worked a full shift on December 18, was off work on December 19 and 20, and worked a full shift on December 21. On December 22, while cutting tongues, he felt a popping or snapping sensation and “a shot of pain go right straight up [his] middle finger.” His left hand then went numb. Meyer stopped working and went to the health department at IBP. The IBP nurse applied ice to Meyer’s hand and kept him in the health center for the remaining forty-five minutes of his shift. Meyer returned to work December 26 and continued to experience swelling in his hand and arm. He notified the health department and was told to go to the hospital.
James Haag, a physician’s assistant at the hospital, noted a flexor strain .in Meyer’s left middle finger and a median nerve injury in his left wrist. Haag restricted Meyer from use of his left hand, fitted him with a brace, and prescribed physical therapy and pain medication. Meyer returned to work, and IBP placed him on light-duty work to accommodate his restriction. Meyer’s pain persisted, and he returned to Haag two days later on December 28. Haag adjusted Meyer’s medication but did not modify his'restriction. On January 25, 2001, Meyer underwent an electromyo-gram (EMG) test by Dr. Brian Sires. The test revealed a diagnosis of carpal tunnel syndrome of the left wrist and left ulnar neuropathy at the elbow. Haag referred Meyer to Dr. Thomas Gorsche, an orthopedic surgeon. Dr. Gorsche suggested eubi-tal-tunnel-release and nerve-transposition surgery as a treatment option for Meyer, but Meyer wanted to take some time to consider the surgery.
Meanwhile, Meyer quit his job at IBP in March 2001. In addition, on April 13, a workers’ compensation examiner for IBP wrote a letter to Dr. Gorsche. In the letter, the examiner asked Dr. Gorsche for his opinion on whether Meyer’s condition could be attributed to “2 days of work activities for IBP.” Dr. Gorsche responded in the negative.
Meyer was then referred to Dr. Gary Knudson, another orthopedic surgeon. Dr. Knudson also diagnosed Meyer with ulnar neuropathy of the left elbow and probable carpal tunnel syndrome of the left wrist. Dr. Knudson opined:
I believe he is suffering from an overuse injury to his left upper extremity precipitated by his work at IBP this past fall and early winter....
Certainly he was only on the job a few months before beginning significant symptomatology, but he may have had a predisposition to develop this symptoma-tology which became manifested after significant repetitive use of his arms at IBP.
Dr. Knudson agreed with Dr. Gorsche that surgery was appropriate.
Following the surgery, Meyer was off work until September 4, 2001. On September 10, 2001, Dr. Knudson performed en-doseopic-carpal-tunnel-release surgery on Meyer. Dr. Knudson released Meyer to regular duty on October 15, 2001.
IBP’s workers’ compensation claims examiner wrote Dr. Knudson a letter on January 14, 2002, asking for his opinion as to whether Meyer’s condition was “causally related to 2 days of work activities for IBP.” Dr. Knudson replied in the negative.
On - May 6, 2002, Meyer saw Dr. Farid Manshadi, a physiatrist, for an independent medical examination, at the request *217 of his attorney. Dr. Manshadi opined that Meyer suffered “cumulative work injury that arose out of and during the course of his work at IBP which resulted in left ulnar nerve neuropathy at the cubital tunnel as well as left carpal tunnel syndrome.” Further, Dr. Manshadi opined that Meyer suffered “a permanent partial impairment of his left upper extremity as a result of the cumulative work injury” of ten percent, which translated to a six-percent whole-body impairment.
Meyer sought workers’ compensation benefits from IBP under Iowa Code chapter 85 (2001), and penalty benefits under section 86.13, by filing a petition for arbitration in June 2001. A hearing was eventually held. In the written decision, the deputy commissioner described the five issues presented for resolution. The first was “whether claimant received an injury that arose out of [and] in the course of his employment with IBP, Inc.”
In resolving this issue, the deputy commissioner relied exclusively on the uncon-tradicted medical testimony “that the two days claimant performed work as an IBP employee prior to December 22, 2000 would not, of itself, have produced his left upper extremity hand and elbow conditions.” The deputy commissioner" also found there was no medical testimony showing that “claimant’s work incident of December 22, 2000 could, of itself, have either caused or materially aggravated claimant’s carpal and cubital tunnel syndromes.” Based solely on this evidence, the deputy commissioner concluded Meyer failed to establish “an injury on December 22, 2000, that arose out of and in the course of his employment with IBP, Inc.” Therefore, the deputy decided the other issues in the claim did not need to be addressed. The commissioner affirmed and adopted the deputy commissioner’s decision.
Meyer sought judicial review. He claimed all the evidence in the record supported a finding that his injury manifested itself on December 22, 2002 and arose out of and in the course of employment, and the commissioner erred by relying on the medical testimony that utilized an improper causation standard.
The district court reversed the decision of the commissioner. It found the conclusion reached by the commissioner that Meyer failed to establish “a compensable injury on December 22, 2000” was not supported by substantial evidence. Instead, the district court determined substantial evidence supported a conclusion that Meyer established an'injury that occurred on December 22, 2000, and that it arose out of and in the course of his employment with IBP. The court was persuaded that the circumstances on December 22, 2000, and those that both preceded and followed- the event; could only mean the injury occurred on December 22, 2000.
IBP filed a notice of appeal and raised a single issue — whether the district court erred in reversing the commissioner’s decision “that Meyer failed to establish that he sustained an injury that arose out of and in the course of his employment” with IBP, Inc. IBP claimed substantial evidence supported the commissioner’s ruling. In the section of its appellate brief addressing the scope of appellate review, IBP stated:
The issue in this appeal has been properly preserved for review as the issue of whether this injury arose out of and in the course of Meyer’s employment with IBP, [I]nc. has been the central issue both in the Workers’ Compensation Commissioner’s decision and the Ruling on Judicial Review.
We transferred the case to the court of appeals. It determined substantial evidence supported the decision of the commissioner. It found the medical testimony *218 presented at the hearing constituted substantial evidence to support the agency’s conclusion that Meyer’s injury was not causally related to his two days of employment with IBP. In addition, the court of appeals stated that Meyer had “pointed to no evidence, medical or otherwise,” that the incident on December 22, 2000 was a manifestation of Meyer’s injury.
Meyer sought further review, claiming the court of appeals “ignored established Supreme Court standards as to when a cumulative injury ‘manifests.’ ” IBP responded that any reliance by Meyer on the cumulative-injury rule was misplaced in this case because the issue on appeal was whether substantial evidence supported the agency’s decision that Meyer’s injury did not arise out of and in the course of employment. IBP further argued that even assuming the cumulative-injury rule was applicable, the rule would support a finding that the injury manifested itself prior to the time Meyer commenced his employment with IBP. We granted further review.
II. Standards of Review
The Iowa Administrative Procedure Act, Iowa Code chapter 17A, governs the scope of our review in workers’ compensation cases. Iowa Code § 86.26. Under the Act, we may only interfere with the commissioner’s decision if it is erroneous under one of the grounds enumerated in the statute, and a party’s substantial rights have been prejudiced. Id. § 17A.19(10).
The issue on appeal has been framed in the context of whether substantial evidence supports the commissioner’s determination that Meyer’s injury did not arise out of and in the course of employment with IBP. However, in fully considering the parameters of our review, we observe that the issue whether an injury arose out of and in the course of employment presents a mixed question of law and fact.
Hawk v. Jim Hawk Chevrolet-Buick, Inc.,
On judicial review, courts are bound by the commissioner’s resolution of the first question — finding the operative facts from the evidence presented — if supported by substantial evidence in the record as a whole.
Excel Corp. v. Smithart,
These different approaches to our review of mixed questions of law and fact make it essential for counsel to search for and pinpoint the precise claim of error on appeal. If the claim of error lies with the agency’s findings of
fact,
the proper question on review is whether substantial evidence supports those findings of fact. If the findings of fact are not challenged, but the claim of error lies with the agency’s interpretation of the
law,
the question on review is whether the agency’s interpretation was erroneous, and we may substitute our interpretation for the agency’s.
Clark,
In this case, the commissioner found from the evidence that Meyer had a cumulative-trauma injury, but concluded the injury did not arise out of and in the course of his employment with IBP because the limited time Meyer worked for IBP (two days) was not the cause, by itself, of the cumulative-trauma injury. Certainly, there was substantial evidence in the record to support the finding that the two days Meyer worked as a IBP employee did not, by itself, cause the injury. These facts are not in dispute. Instead, the actual issue is whether these facts support the commissioner’s conclusion that Meyer’s .injury did not arise out and in the course of employment under the applicable legal standards. 1 Accordingly, our task on judi *220 cial review is to consider if the commissioner either made an erroneous interpretation of the law, or otherwise committed error in applying the law to the facts.
III. Governing Law
Our workers’ compensation statute provides coverage for “all personal injuries sustained by an employee arising out of and in the course of the employment.” Iowa Code § 85.3(1);
accord Meade v. Ries,
With respect to the first requirement of an injury, it is sufficient in this case to recognize that carpal tunnel syndrome is an injury under the workers’ compensation statute.
Noble v. Lamoni Prods.,
The injury element also includes a component of “reasonable definiteness in time.” 3 Larson § 50.01, at 50-2. The reason for requiring a definite date of injury is that a number of important questions often cannot be answered without considering the date of injury, including “which employer and carrier is on the risk.”
Herrera v. IBP, Inc.,
We use the “cumulative-injury rule” to establish the date of injury in repetitive-trauma cases.
McKeever Custom Cabinets v. Smith,
The second requirement means that an employee-employer relationship must exist “at the time of the injury.”
Freeman,
Once a worker is found to have suffered an injury at the time of the employment relationship, the third and fourth requirements must be considered to decide if the injury “ar[ose] out of and in the course of the employment.” Iowa Code § 85.3(1). “Few groups of statutory words in the history of law have had to bear the weight of such a mountain of interpretation as has been heaped upon this slender foundation.” 1 Larson § 3.01, at 3-3. We have contributed to this cordillera of law by our own interpretation of this venerable language:
An injury “arises out of’ the employment if a causal connection exists between the employment and the injury. The injury arises “in the course of’ employment when the injury and the employment coincide as to time, place, and circumstances. Both tests must be satisfied for an injury to be deemed com-pensable.
Meade,
Thus, the “course of employment” element is satisfied when the injury “takes place within the period of the employment, at a place where the employee reasonably may be, and while the employee is fulfilling work duties or engaged in doing something incidental thereto.” 1 Larson at 12.1. In other words, the injury
and the employment must “coincide as to time, place, and circumstances.”
Thayer v. State,
On the other hand, the “arising out of’ employment element has a different focus. It means there must be a “casual relationship between the employment and the injury.”
Koehler Elec. v. Wills,
In applying this arising-out-of element, it is important not to draw in the causation standards applicable to tort law. 4 The *223 concept of proximate or legal cause applicable to tort law is misplaced in determining work-connectedness -under workers’ compensation law. 1 Larson § 3.06, at 3-7.
Larson provides a lengthy explanation:
It is instantly apparent that “arising out of the employment” does not mean exactly the same thing as “legally caused by the employment.” It is true, as many courts and writers have said, that “arising” has something to do with causal connection; but there are many shades and degrees of -causal connection, of which “legal” or “proximate” cause is only one. Taking the words themselves, one is first struck by the fact that in the “arising” phrase the function of the employment is passive while in the “caused by” phrase it is active. When one speaks of an event “arising out of employment,” the initiative, the moving force, is something other than the employment; the employment is thought of more as a condition out of which the event arises than as the force producing the event in affirmative fashion. In tort law the beginning point is always a person’s act, and the act causes certain consequences. In worker’s compensation law the beginning point is not an act at all; it is a relation or condition or situation — namely, employment. No one would suggest that the employer’s only act, the act of hiring the employee, is the operative factor from which all consequences are to be traced. Thus, at the very outset, it. is plain that the attempt to make “arising” equivalent to “causation” is blocked by the words themselves.
One is- next entitled to ask, if the original draftsmen meant to say “caused by the employment,” why did they not do so? The phrase is not only shorter than the “arising” phrase, but much more familiar; it would have come naturally to any draftsman, unless he or she intended to say something different from “caused by.”
Finally, proximate cause or legal cause is out of place in compensation law because, as developed in tort law, it is a concept that is itself thoroughly suffused with the. idea of fault; that is, it is a theory of causation designed to bring about a just result when starting from an act containing some element of fault. The primary test of legal cause in the Ünites States is foreseeability, which is the “fundamental basis of the law of negligence.” Therefore, “if the harm which has actually occurred is one of the particular risks which made the actor’s conduct negligent, it is obviously a consequence for which the actor must be held' legally responsible.” In other words, the essence of the actor’s fault is that, although the consequences of his or her conduct were foreseeable, he or she nevertheless carried on that line of conduct. The foreseeability of the consequences is an inextricable part of the fault-character of the act.
But what relevance has foreseeability if -one is not interested in the culpability of the actor’s conduct? . There is nothing in the theory of compensation liability that cares whether the employer foresaw particular kinds of harm or not. The only criterion is connection in fact with, tjie employment, whether it is foreseeable in advance, or apparent only in retrospect. Thi§ criterion cannot in any *224 logical sense be made to depend on foreseeability. ...
Id.
at 3-7 to 3-8;
accord State Farm Mut. Auto. Ins. Co. v. Rains,
IV. Analysis
With this governing law in mind, we return to the decision of the commissioner. The commissioner had four elements to consider in deciding the initial issue presented at the hearing: (1) Did Meyer sustain an injury (injury element)? (2) Did Meyer and IBP have an employer-employee relationship at the time his injury occurred (employment-status element)? (3) Was the injury related to the working environment or conditions of the job (arising-out-of-employment element)? and (4) Did the injury coincide with the time and place of employment (course-of-employment element)? Failure of proof of any one of these elements would have taken Meyer’s claim out of the statutory coverage formula for compensability. In considering the first element, the commissioner found from the evidence that Meyer sustained a cumulative-trauma injury. However, the commissioner skipped the second and fourth elements and proceeded directly to the third element. The commissioner did not apply the cumulative-injury rule to decide the date of the injury, or decide that Meyer’s injury manifested before his employment with IBP commenced. Instead, the commissioner only addressed the arising-out-of element and found that two days of work for IBP could not, by itself, have produced Meyer’s injury. The commissioner found a failure of proof on the arising-out-of element based solely upon the medical opinions by Drs. Gorsche and Knudson that Meyer’s two days of work for IBP was not, by itself, the cause of the injury.
The undisputed evidence in the case revealed that the particular job performed by Meyer during his two days of employment with IBP was the same job performed for his prior employer. It involved repetitive hand and arm motions, conditions that are known to lead to carpal tunnel syndrome or cumulative-trauma injury. It was undisputed that Meyer sufr fered this type of injury. Thus, although Meyer only worked a short time on the job, the type of injury he sustained was nevertheless a “rational consequence” of a hazard of the work he performed with IBP.
Koehler Elec.,
Under the arising-out-of element decided by the commissioner, Meyer was only required to “prove that a condition of his employment increased the risk of injury.”
Koehler Elec.,
The error committed by the commissioner also reveals the error committed by the district court. In our judicial review of workers’ compensation cases, we review the district court decision to decide if our legal conclusions mirror those reached by the district court.
Cargill, Inc. v. Conley,
As revealed by our analysis in this case, the basic issue turns on whether Meyer’s injury manifested before or after he became an IBP employee. However, the commissioner never found any facts to support a conclusion that the injury manifested before or after Meyer became an IBP employee, and this question cannot be decided on judicial review as a matter of law because the evidence clearly could support two reasonable conclusions. We have said that the commissioner commits error by failing to weigh and consider all of the evidence, and the remedy on judicial review for this type of error is to remand the case for a decision by the commissioner on the existing record, not for the district court to find the facts and make the decision.
Armstrong,
*226 The record reveals a conflict in the evidence regarding the time when the injury-sustained by Meyer manifested. There is evidence that could support a finding that the injury occurred before Meyer commenced work for IBP and there is evidence to support a finding it occurred after he commenced work for IBP. Thus, remand is necessary for the commissioner to reevaluate the evidence and decide this question in light of the relevant law, as well as all other questions that may follow.
V. Conclusion
We vacate the decision of the court of appeals. We reverse the district court judgment and remand the case to the workers’ compensation commissioner for further proceedings consistent with this opinion.
DECISION OF COURT OF APPEALS VACATED; DISTRICT COURT JUDGMENT REVERSED AND REMANDED.
Notes
. Although a claim of insubstantial evidence is usually used to challenge findings of fact, we understand how it can be implicated, as in this case, in a challenge to a legal conclusion. Error occurs when the commissioner makes a legal conclusion based on facts that are made-
*220
quate to satisfy the governing legal standards. Yet, a claim of insubstantial evidence to support a legal conclusion does not give rise to the standard of review applicable to the claim of substantial evidence to support the factual findings by the commissioner. When the commissioner takes a piece of evidence and uses it to draw a legal conclusion to improperly deny compensation, we do not review the conclusion by looking at the record as a whole to see if there was substantial evidence that could have supported the ultimate decision, as argued by IBP in this case. Instead, we review the decision made. If the commissioner fails to consider relevant evidence in making a conclusion, fails to make the essential findings to support the legal conclusion, or otherwise commits an error in applying the law to facts, we remand for a new decision unless it can be made as a matter of law.
See Armstrong v. State of Iowa Bldgs. & Grounds,
. In addition to the requirement of an injury, we have said that our workers' compensation act primarily requires the worker to establish: "(1) an employer-employee relationship at the time of the injury, (2) an injury arising out of and in the course of employment, and (3) the disability ... proximately caused by the injury.”
Freeman,
. We, of course, recognize certain rules that may impose responsibility on an employer for conditions that predated the employment or for the aggravation of prior injuries.
See Excel Corp.,
. We have on occasion injected the term “proximate cause” into workers’ compensation cases by stating that the employee must prove that "the injury is a proximate cause of the claimed disability.”
Grundmeyer,