The employee appeals from the judge’s finding that the employee did not sustain an injury arising out of and in the course of his employment with the employer.  We affirm.

The employee worked for Imperial Plastics, Inc. [the employer], for 22 years.^[1]  On April 20, 2009, he was seen by Dr. Steve Lawler, complaining of having experienced pain in the right lower back for about a week.  The doctor’s records indicate, “No specific injury-pain just came on.”  The employee was diagnosed with low back pain.  The employee called in sick to work between April 20 and April 24, 2009.  He returned to his normal job on or about April 27, 2009.

On May 6, 2009, the employee received treatment at Noble Chiropractic Clinic.  At that time, he complained of right low back/hip pain that radiated into his anterior thigh.  Clinic records for that date indicate, “onset- 1 month ago, unknown origin.  Pt works with plastic molds-often is having to climb up onto machine or crawl underneath to fix something.  Also active outdoorsman.”  Chiropractic care did not alleviate his symptoms.

The employee was seen by Dr. Richard Hadley on May 13, 2009, complaining of back pain radiating down the right thigh and down the anterior aspect of the lower part of that leg.  According to treatment notes, “he has had some back pain for a considerable period of time.  He is unable to recall exactly how much, but he has had leg pain for about a month.”  An MRI, performed on May 15, 2009, showed a large right posterolateral L3-4 disc herniation with impingement of the L3 nerve root, slight displacement of the right L4 nerve root, and degenerative changes at L2-3.  Dr. Hadley administered an epidural steroid injection, but the employee experienced very little relief, and the employee subsequently underwent a laminectomy and disc excision at L3-4 on the right, on June 2, 2009.  Following that surgery, the employee was able to return to work without restrictions.

On May 15, 2009, the employee completed an Employee’s Report of Injury, indicating that he had sustained a work injury on April 17, 2009.  When asked to describe what caused his injury, he wrote, “lot of walking from each end of building continuous climbing up and down of machines.”  He also indicated that he did not notify his supervisor of the injury because “I felt some pain in leg.  Thought was just a muscle strain that would get better on its own.  Sucked it up and kept working.”  Under additional comments, he wrote, “20+ years of cement floors climbing up & down of machines.”

At his pre-op physical on May 29, 2009, the employee reported that he had first noticed back pain when he jumped off a machine at work on April 17, 2009.

On November 30, 2009, Dr. Hadley responded to a letter from the employee’s attorney, stating, “On the basis of the history that I obtained from [the employee], I am unable to document that his work was a substantial and contributing factor to his condition.”  In a subsequent letter dated March 15, 2010, Dr. Hadley stated that the employee “has since indicated that his symptoms were precipitated by jumping off of a platform.”  The doctor had also indicated that he had reviewed a witness statement from Bryan Patterson, who purportedly indicated that he and the employee would “frequently”^[2] jump off platforms at work and that the employee had said to him “that he had noted onset of back and leg pain after jumping off of a platform.”  Dr. Hadley then wrote,

Dr. Charles Burton performed an independent medical examination for the employer and insurer on June 28, 2010.  Dr. Burton noted that the “key issue” was whether or not a work injury had occurred given the contemporaneous medical records indicating no specific injury.  He went on to opine that the alleged jumping incident on April 17, 2009, was not a substantial contributing cause of the L3-4 disc herniation and diagnosed the employee with “multilevel degenerative disc pathology.”

When the matter proceeded to hearing, the employee claimed a specific injury occurring on April 17, 2009, when he allegedly jumped off a machine platform onto the floor at work.  The employee testified that he felt a “little pop” and had pain in his right upper leg at that time.  He also testified that he did not talk about this incident with Mr. Patterson on the date it occurred.  In support of his claim, the employee introduced medical records, the letters of Dr. Hadley, and the deposition testimony of Bryan Patterson.  The deposition was submitted to the court on July 30, 2013, and the record closed on that date.

In findings and order filed on July 31, 2013, the compensation judge found that the employee’s testimony was not credible, that he did not sustain a work-related injury on April 17, 2009, and that the employee’s diagnosis is multilevel degenerative disc disease.  The employee appeals.

On appeal, the Workers’ Compensation Court of Appeals must determine whether “the findings of fact and order [are] clearly erroneous and unsupported by substantial evidence in view of the entire record as submitted.”  Minn. Stat. § 176.421, subd. 1 (2012).  Substantial evidence supports the findings if, in the context of the entire record, “they are supported by evidence that a reasonable mind might accept as adequate.”  Hengemuhle v. Long Prairie Jaycees, 358 N.W.2d 54, 59, 37 W.C.D. 235, 239 (Minn. 1984).  Where evidence conflicts or more than one inference may reasonably be drawn from the evidence, the findings are to be affirmed.  Id. at 60, 37 W.C.D. at 240.  Similarly, findings of fact should not be disturbed, even though the reviewing court might disagree with them, “unless they are clearly erroneous in the sense that they are manifestly contrary to the weight of evidence or not reasonably supported by the evidence as a whole.”  Northern States Power Co. v. Lyon Food Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).

The employee contends that substantial evidence does not support the judge’s finding that the employee’s testimony at hearing was not credible.  We are not persuaded.

The employee’s testimony about a specific injury allegedly occurring on April 17, 2009, was contrary to all of the contemporaneous medical records.  In fact, he repeatedly indicated to the medical providers that he did not know how his symptoms had begun.  His hearing testimony is also contrary to the information he provided on his report of injury.

The employee testified that he did not report an injury because he thought he had sprained his leg and did not know that he had injured his back.  But this testimony is also contrary to the medical records.  Dr. Lawler’s records reflect that the employee complained of right-sided low back pain on April 20, 2009.  Noble Chiropractic records note that the employee complained, in part, of ongoing right-sided low back pain on May 6, 2009.  According to Dr. Hadley’s records of May 13, 2009, the employee reported that he had been experiencing back pain for months.

Assessment of a witness’s credibility is a unique function of the trier of fact.  Even v. Kraft, Inc., 445 N.W.2d 831, 42 W.C.D. 220 (Minn. 1989) (citing Brennan v. Joseph G. Brennan, M.D., 425 N.W.2d 837, 839-40, 41 W.C.D. 79, 82 (Minn 1988)).  Substantial evidence supports the judge’s finding that the employee’s testimony was not credible.

The employee argues that the compensation judge erred as a matter of law in failing to address the testimony of Mr. Patterson in detail, contending that this testimony “tips the scale” and demonstrates that the employee sustained a work-related injury on April 17, 2009.  Again we are not persuaded.

This court has long held that a judge is not obligated to discuss or mention every piece of evidence submitted in a case.  Regan v. VOA Nat’l Housing, 61 W.C.D. 142 (W.C.C.A. 2000).  It is clear that the judge had the deposition, as it is marked as an exhibit, recorded on the exhibit list, and mentioned in the findings and order as having been received on July 20, 2013.  We would also observe that Mr. Patterson’s testimony was sometimes vague and sometimes conflicted with other evidence on the issue.              During direct examination, Patterson was given the opportunity to review a statement he had given on February 16, 2010, ten months after the employee’s alleged injury.^[3]  Patterson testified that he believed the statement to be true and accurate.  However, he went on to testify that he was a meth addict until July 5, 2009, that “my past before that was insanely bad,” that he did not witness the alleged injury but that he talked to the employee about his condition on the date of injury, that he did not know the date of injury but guessed it was sometime in 2010, and that the employee had said he hurt his back coming down the ladder or stairs, but Patterson could not remember if the employee was walking or jumping.

The judge did not err by failing to discuss this testimony.

The employee contends that substantial evidence does not support the judge’s finding that the employee did not sustain a work-related injury to his low back on April 17, 2009.  We disagree.

The employee’s own doctor opined only that “if” it was determined that the employee had jumped off the platform and experienced immediate back and leg pain, “then” it would be his opinion that the work activities contributed to the employee’s herniated disc.  The judge found the employee’s testimony regarding the onset of symptoms to be lacking in credibility.  As such, there is no medical opinion that in any way supports a finding of a work injury.  The record as a whole clearly supports the judge’s denial of the employee’s claim.

Finally, the employee contends that Dr. Burton’s opinion should not have been received into evidence, and he disputes the doctor’s diagnosis of multilevel degenerative disc disease.  Given our affirmance of the judge’s decision as to the occurrence of a work injury, we need not address this argument.