The dispositive issue in this case is whether Linda K. Helm (Helm) failed to meet the burden of proof assigned to her under Pederson v. State ex rel. Wyoming Workers’ Compensation Din, 939 P.2d 740, 742 (Wyo.1997). Specifically, the hearing examiner decided that Helm failed to demonstrate that carpal tunnel syndrome, claimed as a subsequent injury, was causally related to an original, covered injury to her knee. The failure of proof is subject to the rule on review testing whether the decision was arbitrary, capricious, an abuse of discretion, or contrary to law. Helm phrases the problem in alternative ways, but the determination that she failed to prove the causal connection between the two medical conditions structures the issue. The record in this case captures conflicting expert opinions on the issue of causation. Causal connection is a question of fact, and the function of determining the credibility of the witnesses and weighing the evidence is assigned to the hearing examiner. In a case such as this, the decision of the hearing examiner will be overturned only if it is clearly contrary to the great weight of the evidence. It is not. The Order Denying Benefits, premised on the failure of Helm to carry her burden of proof, is affirmed.
In the Brief of Appellant, the issues that are raised are:
I. Whether a subsequent injury sustained by a claimant, which is causally related to an existing compensable injury, should also be compensated by the Wyoming Workers’ Safety and Compensation Division?
II. Whether the hearing examiner’s decision denying benefits to appellant, Linda K. Helm, is arbitrary, capricious, contrary to law or supported by substantial evidence?
This Statement of the Issues is found in the Brief of Appellee, State of Wyoming, ex rel., Wyoming Workers’ Safety and Compensation Division (Division):
State ex rel. Wyoming Workers’ Safety and Compensation Division:
The Employee injured her left knee at work, she suffered more that fifty intervening falls, and more than a year later *1238she injured her right wrist in a fall on the stairs in her house.
A. Was the denial of benefits for carpal tunnel syndrome supported by substantial evidence, within the Hearing Examiner’s discretion, and in accordance with law.
On September 6, 1995, Helm, who then worked as a waitress in a Cheyenne truck stop, slipped on a wet floor at work, causing an injury to her left knee. The course of treatment of that injury was premised upon an MRI obtained on October 10, 1995, which apparently indicated, among other things, that her anterior cruciate ligament (ACL) was intact. Her treating physician attempted rehabilitation and conservative treatment, but Helm continued to have problems with her knee. Almost a year later, another MRI was conducted on September 11,1996, which disclosed a complete tear of the ACL. Helm’s physician concluded that this tear was causally related to the fall she had sustained at work.
The Division arranged for an independent medical evaluation by another physician. The physician employed by the Division also opined that the tear of the ACL was related causally to the original injury:
As to whether the original injury of September, 1995 resulted in the problems she is experiencing, due to the fact the patient has had no other specific injury over the course and is continually symptomatic, I would conclude the ACL tear is due to her original injury. As to why the MRI scan of 1995 was normal, MRI’s are not entirely sensitive for cruciate ligament injuries. She may have had either a partial tear or the MRI missed the tear of the ACL, which may have been present since her initial injury. At any rate, due to the lack of another significant injury, I think the ACL tear was present after the initial injury. Therefore, the problems she is experiencing are directly related to her original injury to her left knee.
Following this examination, the Division agreed to pay for corrective surgery and treatment of the torn ACL.
On either November 24 or 25 of 1996, Helm sustained a fall while descending the stairs in her home. When she saw her treating physician a few days later, she also complained of intermittent numbness in her right arm. The numbness persisted, and her physician diagnosed the condition as Carpel Tunnel Syndrome (CTS). The physician concluded that Helm’s problem with her ACL had caused her to fall at home and that fall, in turn, resulted in her suffering from CTS. When this information was presented to the Division, it sent Helm’s file to still another physician for a chart review. Based upon his review of the chart, the third physician concluded that Helm’s CTS was not work related. Following that assessment, the Division denied the claim for benefits for CTS submitted by Helm.
Helm requested a hearing on the final determination relating to her claim for CTS. On July 2, 1997, that hearing occurred before a hearing examiner of the Office of Administrative Hearings. Helm testified on her own behalf, and she also called her daughter as a witness. She also offered six exhibits: (1) the deposition of her treating physician; (2) a letter from the Division to the second physician requesting an evaluation of Helm; (3) the independent medical evaluation by the second physician; (4) the final determination letter dated September 27,1995; (5) the final determination letter dated November 15, 1996; and (6) the final determination letter dated March 3, 1997. All of Helm’s exhibits were received into evidence by the hearing examiner.
The Division called no witnesses at the hearing. Instead, counsel for the Division conducted cross-examinations of Helm and her daughter, and the Division introduced five exhibits of its own: (a) the emergency room report dated September 6, 1995; (b) the chart review by the third physician; (c) the treatment record from Helm’s treating physician; (d) the progress report from the Platte County Memorial Hospital dated January 7, 1997; and (e) the report of Cheyenne Radiology and MRI dated September 11, 1996. Like Helm’s exhibits, the Division’s exhibits were received into evidence.
The evidence most favorable to the Division’s determination to deny benefits is the *1239review of the medical records made by the third physician. In the course of that review, the third physician was asked, “[c]ould a fall cause carpal tunnel syndrome?” His response was:
Carpal tunnel is generally considered a repetitive use type of syndrome. It is my opinion that it could not occur with just one fall. Therefore, I cannot relate the carpal tunnel to the work-related injury in September of 1995.
In addition to the testimony of the third physician, the Division established by cross-examination of Helm’s daughter that Helm engaged in craft hobbies, including crocheting, which could involve repetitive hand and wrist motions.
At the hearing, most of the Division’s evidence and its argument focused on a demonstration of the proposition that Helm’s ACL tear was not related to the fall she sustained at work. The natural extension of that theory is that the fall on the stairs at home was not work related, and, even if the CTS was a product of the fall on the stairs, it did not result from her injury at work. The Division supported this position with the treatment records of the treating physician, which indicated that Helm’s cruciate ligament was intact on her initial visit. The treating physician also testified in his deposition that although he believed the ACL tear was a product of the work injury, he could not actually prove that fact.
The third physician, from a review of the record, presented a contrary conclusion to those of the treating physician and the physician who examined Helm on behalf of the Division. The doctor explained his conclusion at some length:
There was really no instability to the knee noted until quite some time after the September 1995 injury. The instability was not noted until the slip and fall which occurred almost one year after the original work-related injury. If she did have a partial tear and the MRI was not sensitive to it, there certainly should have been an effusion accompanying that, and this goes against the initial MRI report. It suggests that there could have been an internal derangement of the knee. With the lack of effusion, which would have signified some injury, even if there was a partial injury, it is my opinion that some level of effusion should have been present. It is very hard to believe that she may have had a partial tear with a normal ligamentous examination that progressed to a complete tear on an MRI a year later. Therefore, I would have a hard time conceptualizing and believing that the second MRI showed a complete anterior cruciate ligament deficient knee and an unstable knee which was giving way and that it would be related to her September 6,1995 injury. In my opinion, the only plausible explanation is that there was another intervening injury and that injury caused the knee to be completely unstable and caused an anterior cruciate ligament to be torn across.
It is also my opinion that the fact that she now has an anterior cruciate ligament that is completely torn * * * does not appear to be compatible or consistent with the examinations that have been rendered to her. The initial MRI report showed no effusion, normal findings, and is now compared to what is now later being identified as a completely torn anterior cruciate ligament and unstable knee. Therefore, it is my opinion that another injury must have occurred and her current condition is not related to her work injury of September 6, 1995.
After the hearing, the hearing examiner ruled in favor of the Division. In the conclusions of law, the hearing examiner stated:
7. Helm has failed to meet her burden in that she has failed to establish a causal nexus between the knee injury in 1995 and the [CTS] condition in 1996. From the time of her original knee injury to the November 1996 fall, Helm fell at least 50 times. None of these were at work with Flying J Oil Company and the fall in November was in Helm’s house. Helm worked as a waitress and this work requires extensive repetitive motion. This Office is not persuaded that the work injury in 1995 caused Helm’s knee to go out and that when she fell in November 1996 it caused her [CTS] condition. Too much time has passed between the two injuries, *1240there are two different body parts involved and Helm’s work as a waitress is more likely the cause of the [CTS] than a single fall.
Helm sought review of the Order Denying Benefits in the district court, and the case was certified to this Court in accordance with W.R.A.P. 12.09.
Helm suggests that this Court should reevaluate the evidence included in the record of the administrative hearing and substitute our judgment for that of the hearing examiner. We do not apply our substantial evidence rule in that way because the rule limits this Court to analyzing the record to determine if there is evidence from which a reasonable person could find the fact or facts as found by the hearing examiner. The relationship between the substantial evidence rule as it pertains in administrative proceedings and the rule that is used when the agency concludes that there has been a failure of proof has produced some consternation. These rules are not mutually exclusive. The substantial evidence rule is invoked to determine the validity of the factual findings by the agency. The failure of a factual finding on a material issue to be supported by substantial evidence leads to a conclusion that error is present in the proceedings. Assuming, as we determine is true here, that the findings of fact are supported by substantial evidence, we then test whether the agency determination that a claimant failed to meet the burden of proof assigned to her is arbitrary, capricious, an abuse of discretion, or otherwise not supported by law.
In a worker’s compensation matter, we said recently:
A claimant for worker’s compensation benefits has the burden of proving all the essential elements of the claim by a preponderance of the evidence in the contested case hearing. Martinez v. State ex rel. Wyoming Workers’ Compensation Div., 917 P.2d 619, 621 (Wyo.1996). When an agency decides that the party charged with the burden of proof has failed to meet that burden, the case is reviewed under the “[a]rbitrary, capricious, an abuse of discretion or otherwise not in accordance with the law” language of Wyo. Stat. § 16—3—114(e)(ii) (1990). City of Casper v. Utech, 895 P.2d 449, 452 (Wyo.1995). On appeal the complainant * * * has the burden of proving arbitrary administrative action. Knight v. Environmental Quality Council of State of Wyo., 805 P.2d 268 (Wyo.1991); Wyoming Bancorporation v. Bonham, 527 P.2d 432, 439 (Wyo.1974); Marathon Oil Co. v. Welch, 379 P.2d 832, 836 (Wyo.1963); Whitesides v. Council of City of Cheyenne, 78 Wyo. 80, 319 P.2d 520, 526 (1957). The agency, as the trier of fact, is charged with weighing the evidence and determining the credibility of witnesses. Utech, 895 P.2d at 451, and cases there cited. The deference normally accorded to the findings of fact by a trial court is extended to the administrative agency, and the agency’s decision as to the facts will not be overturned unless it is clearly contrary to the overwhelming weight of the evidence. Wyoming Steel & Fab, Inc. v. Robles, 882 P.2d 873, 875 (Wyo.1994).
Pederson, 939 P.2d at 742.
Applying the Pederson standard, we do not disturb the decision of the hearing examiner unless a claimant, in this instance Helm, can demonstrate that it was arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law. This rule affords the petitioner the opportunity to show that the findings of fact1 were contrary to the overwhelming weight of the evidence. When an agency’s action or decision is “based on a consideration of relevant factors and is rational,” we will not rule that the *1241action or decision is arbitrary or capricious. Mortgage Guaranty Ins. Corp. v. Langdon, 634 P.2d 509, 520 (Wyo.1981).
Helm, as a claimant of worker’s compensation benefits, was charged with the burden of establishing each element of her claim. Shassetz v. State ex rel. Wyoming Workers’ Safety and Compensation Div., 920 P.2d 1246, 1248 (Wyo.1996) (quoting Padilla v. Lovern’s, Inc., 883 P.2d 351, 354 (Wyo.1994)). Even though Helm asserts that the burden shifted to the Division after she made a prima facie case, the burden of proof does not shift to the Division. Shassetz, 920 P.2d at 1250; Johnson v. State ex rel. Wyoming Workers’ Compensation Div., 911 P.2d 1054, 1061-62 (Wyo.1996); Casper Iron & Metal, Inc. v. Unemployment Ins. Com’n of Dept. of Employment of State of Wyo., 845 P.2d 387, 393 (Wyo.1993). Properly assigning the burden of proof to Helm, the hearing examiner ruled that she had failed to meet that burden and had failed to prove a causal relationship between her fall at work and her CTS. That determination is exclusively within the province of the hearing examiner, and we defer to his judgment. Pederson, 939 P.2d at 742. The evidence in this case provided a rational basis for the hearing examiner to conclude that Helm had failed to establish that causal connection by a preponderance of the evidence. This decision was neither arbitrary nor capricious. It did not manifest an abuse of discretion, nor can it be said that it was otherwise not in accordance with law. It is not contrary to the overwhelming weight of the evidence. In such an instance, this Court does not re-weigh the evidence because that function is exclusively the province of the hearing examiner. Pederson, 939 P.2d at 742-43.
The Order Denying Benefits entered by the Office of Administrative Hearings is affirmed.
. Although the hearing examiner labeled his finding that Helm's CTS was not work related as a conclusion of law, it is more properly a finding of fact. In such cases, this Court will review findings in their proper category, regardless of how the hearing examiner has labeled them. Billings v. Wyoming State Bd. of Outfitters and Professional Guides, 837 P.2d 84, 87 (Wyo.1992). See also Kilmer v. Dillingham City School Dist., 932 P.2d 757, 764 n. 8 (Alaska 1997) and Battaglia Properties, Ltd. v. Florida Land and Water Adjudicatory Com'n, 629 So.2d 161, 168 (Fla.App.1993). Lest there be any doubt, we reiterate that the question of whether an injury occurred in the course of employment is a question of fact. Cabral v. Caspar Bldg. Systems, Inc., 920 P.2d 268, 269 (Wyo.1996).