The employee appeals from the compensation judge’s finding that a claimed injury, an umbilical hernia, did not arise out of his employment.  We affirm.

Juan Perez, the employee, began employment at Arby’s, the employer, in October 2002 and worked there until January or February 2010.  The employee contends that on October 15, 2009, he developed a hernia as a result of his work as a maintenance worker for the employer.  The employer and its insurer denied liability.  On the date of the alleged injury, the employee was also employed by Packer Sanitation Services, under the name Rigoberto Mata.

On October 28, 2009, the employee was seen by Kimberly Figueroa PAC at West Side Community Health Services.  The office note reflects that the employee had experienced symptoms of an umbilical hernia for a week and that the employee lifted product and garbage at work.  On November 11, 2009, the employee was seen by Dr. Christopher Nielsen for a surgical consultation at the request of Ms. Figueroa.  The doctor reported the employee was “an employee at Arby’s Restaurant and suffered an event on 10/30/2009 associated with work activities providing maintenance wherein he developed painful umbilical bulging.”  (Pet. Ex. E.)  The doctor recommended an open umbilical hernia repair with implantation of mesh.  By report dated March 18, 2010, Dr. Jessica Pereira stated that the onset of the employee’s umbilical hernia was October 1, 2009.

In May 2010, the employee was examined by Dr. Matthew Melin, at the request of the employer and insurer.  The doctor recorded that the employee had been picking up garbage bags and throwing them into a dumpster at work on October 15, 2009.  The employee stated that, as he was throwing a 20-40 lb. bag, he felt a sudden sharp stabbing pain in his mid abdomen.  The employee also told the doctor that he also worked at Packer Sanitation, in a cleaning capacity, but that the job involved no lifting.  Dr. Melin opined the employee sustained an umbilical hernia arising out of his employment with the employer on October 15, 2009.

The employee filed a claim petition seeking payment of wage loss benefits and medical expenses resulting from an alleged October 15, 2009, personal injury with the employer.  The evidence at the hearing included the testimony of the employee and of Alberto Rodriguez, a coworker, together with the deposition testimony of Rob Thyne, the store manger for the Arby’s Restaurant at which the employee worked.  Following a hearing, the compensation judge found that, on or about October 15, 2009, the employee sustained an injury in the nature of an umbilical hernia.  The judge also found, however, that the employee failed to prove this injury arose out of and in the course of his work at Arby’s.  Accordingly, the judge denied the employee’s claim.  The employee appeals.

The compensation judge’s findings and order includes a memorandum, which states:

On appeal, the employee argues that the compensation judge erred in denying his claim, contending that all of the contemporaneous medical records, along with the report of Dr. Melin, support the conclusion that he sustained a work-related injury.  Further, the employee argues, the First Report of Injury prepared on October 19, 2009, is consistent with his testimony that he sustained an injury at work.  In addition, the employee argues that the judge’s reliance on the testimony of Mr. Rodriguez was clearly erroneous because Mr. Rodriguez refused to answer questions about his legal status.  Also, the employee argues, Mr. Rodriguez was biased due to the fact that the employee fired Mr. Rodriguez from his job at Packer Sanitation.  For these reasons, the employee contends, the evidence does not support the compensation judge’s decision.  We are not persuaded.

The deposition of Robert Thyne was taken on February 22, 2011, because he was not available to testify at the hearing.  Mr. Thyne testified that on Monday, October 19, 2009, the employee told him that he had injured himself, causing a hernia.  The employee also told Mr. Thyne that he thought he had injured himself working at Arby’s.  Mr. Thyne then asked the employee how he knew he injured himself at Arby’s and whether he could have injured himself at his job at Packer Sanitation.  The employee replied that he could not have injured himself at Packer Sanitation because he did not do heavy lifting at that job.  When Mr. Thyne asked the employee when he had hurt himself, the employee stated that he was uncertain.  Mr. Thyne testified that the employee might have told him that the injury had occurred sometime the previous week, or he might have said that he did not know, but, in any event, the employee did not give Mr. Thyne a specific date.  Mr. Thyne also testified that, during that conversation, the employee did not tell him how he had injured himself.

Following his conversation with the employee, Mr. Thyne consulted his supervisor about the claimed injury and was told to report the injury to the risk management department.  Sometime thereafter, Mr. Thyne again spoke with the employee, who stated that he had injured himself taking out the trash.  On Wednesday, October 21, 2009, Mr. Thyne spoke with Angela Warring, in the employer’s risk management department, and provided her with information concerning the employee’s claimed injury.  Sometime later, someone prepared a First Report of Injury, which described circumstances of the injury as “EE was lifting a large bag of trash into the trash can.  Thought he strained at first but now he thinks he has a hernia.”  (Pet. Ex B.)  Mr. Thyne testified that two of the employee’s coworkers later came to him to report that they had been asked by the employee to state that they had seen the employee hurt himself.  According to Mr. Thyne, these coworkers said that they reported this conversation to him because they did not think what the employee was asking was right.

Mr. Rodriguez testified at the hearing that the employee gave him several different versions of what he had been doing when he injured himself at Arby’s, including removing a filter from the fryer, putting away soda boxes, emptying the shake machine, and unloading product from a truck.  Mr. Rodriguez testified that the employee told him on another occasion that he was not sure that he gotten injured at Arby’s, and he testified that the employee had never told him that he had injured himself lifting trash bags at Arby’s.  He further testified that the employee had asked him to be a witness concerning his injury.  When asked on direct examination what the employee had said, Mr. Rodriguez testified as follows:

The compensation judge found the employee’s testimony was unpersuasive in view of the sketchy and conflicting details the employee gave to Mr. Thyne and Mr. Rodriguez.  The judge also concluded that the evidence strongly suggested that the employee did not know the cause of his hernia and was simply guessing.  Much of the testimony of Mr. Thyne and Mr. Rodriguez support the judge’s conclusion.  Also, Mr. Rodriguez testified the employee told him that he intended to bring a claim against Packer Sanitation if Arby’s did not pay.  This testimony calls into question the employee’s credibility and therefore any causal connection between his hernia and his work activities with the employer.

The employee fired Mr. Rodriguez from his job at Packer Sanitation, and Mr. Rodriguez refused to answer when asked whether he was legally entitled to be in the United States.  The employee contends that his firing of Mr. Rodriguez caused Mr. Rodriguez to be biased against him and that the compensation judge erroneously failed to draw an adverse inference from Mr. Rodriguez’s refusal to answer the question about his legal status.  For these reasons, the employee contends the compensation judge erred in relying on the testimony of Mr. Rodriguez.  We disagree.

The question of whether the employee’s hernia arose out of and in the course of his employment with the employer turns primarily on the testimony of the employee, Mr. Thyne, and Mr. Rodriguez.  Assessment of the credibility of a witness is the unique function of the trier of fact.  Brennan v. Joseph G. Brennan, M.D., P.A., 425 N.W.2d 837, 839-40, 41 W.C.D. 79, 82 (Minn. 1988).  It is not the role of this court to evaluate the credibility and probative value of witness testimony or to choose different inferences from the evidence than the compensation judge.  Krotzer v. Browning-Ferris/Woodlake Sanitation Serv., 459 N.W.2d 509, 513, 43 W.C.D. 254, 260-61 (Minn. 1990).  A finding based on credibility of a witness will not be disturbed on appeal unless there is clear evidence to the contrary.  See Even v. Kraft, Inc., 445 N.W.2d 831, 835, 42 W.C.D. 220, 225-26 (Minn. 1989).  We find no clear evidence to the contrary.  While the compensation judge could have rejected the testimony of Mr. Rodriguez for the reasons cited by the employee, the judge was not required to do so.

The compensation judge’s determination that the employee failed to prove a causal relationship between his work activities with the employer and his umbilical hernia is supported by substantial evidence.  Accordingly, this court must affirm that decision.  Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235, 239 (Minn. 1984).