Kantor Electric, Inc., and its insurer appeal from the compensation judge’s decision denying their request for reimbursement from the City of International Falls.  We affirm.

The employee was employed as an electrician for Kantor Electric, Inc., for more than 20 years,^[1] working on commercial and residential construction and remodeling projects.  The job at times required heavy lifting and the need for the employee to use his arms above his head.  Beginning in about 1988, the employee also worked as a volunteer firefighter for the City of International Falls [the City].

On the evening of November 26, 1997, the employee sustained an injury to his left shoulder while helping a fellow firefighter who had fallen through the floor while fighting a fire.  Because an air tank was caught on the edge of the hole, the employee had to yank up on his colleague several times to free him.  The employee estimated that the man may have weighed 250 pounds, including fire gear.  The employee testified that he began noticing soreness in his left shoulder as soon as he left the fire scene.

On December 5, 1997, the employee sought care for shoulder pain from Dr. James Berlin.  Dr. Berlin noted that the employee “seem[ed] to have full range of motion,” and he found no grating or grinding or areas of particular tenderness in the shoulder joint itself, but the employee did exhibit some tenderness “in the trap muscle.”  Dr. Berlin diagnosed shoulder strain, noting specifically that “[t]his does not appear to be a significant injury and I fully expect this to heal.”  The doctor went on to observe that such injuries typically took four to six weeks to heal completely and that the employee was to return if not significantly improved by then.  The employee was advised that he could perform “normal activity” within the limits of his pain.

The employee testified that his shoulder symptoms improved somewhat but never resolved entirely and that he modified the way he worked to avoid aggravating his symptoms.  However, he missed no time from either job and sought no additional care for his left shoulder condition for nearly 12 years.  He explained at hearing that he had heard horror stories about treatment for shoulder injuries and had decided to tough it out without treatment for as long as he could.

On April 21, 2009, the employee was seen by Dr. Steven Phillipson “for evaluation of an injury that started while lifting another firefighter out of broken flooring in 1997.”  According to treatment notes from that evaluation, the injury had “been getting progressively worse for the last 11 years,” and the employee’s overhead work as an electrician had been getting more difficult due to pain.  The employee testified that he had been pulling heavy wire on a job for Kantor and that his shoulder symptoms had begun to interfere with his sleep, leading him to seek treatment.

In November 2009, the employee was seen by Dr. Troy Erickson, an orthopedic surgeon.  The employee told Dr. Erickson that his left shoulder symptoms really flared up due to his work as an electrician.^[2]

On January 13, 2010, Dr. Erickson performed arthroscopic surgery on the employee’s left shoulder, including a labral repair, subacromial decompression, and excision of the distal clavicle.  According to the surgical report, the employee’s preoperative and postoperative diagnoses were the same:  left rotator cuff tendinitis, impingement syndrome, AC arthritis, and labral tear.  The surgery was successful, and the employee was ultimately able to return to work with no restrictions.

On October 12, 2011, the employee underwent an independent medical examination by Dr. Sheldon Segal, at the request of Kantor Electric.  Dr. Segal concluded that the employee’s 1997 injury as a volunteer firefighter had likely caused the labral tear and that the injury and the employee’s work for Kantor were equally responsible for the employee’s disability and need for treatment in 2009.

The employee was also examined by Elmer Salovich, at the request of the City of International Falls.  Dr. Salovich concluded that the 1997 injury was not a substantial contributing cause of the employee’s left shoulder condition, which in his opinion had resulted from the employee’s repetitive overhead work in his job as an electrician for Kantor.

Kantor and its insurer admitted liability for a Gillette injury^[3] culminating on March 1, 2009, and sought contribution or reimbursement from the City, contending that the employee’s 1997 work injury was a substantial cause of the employee’s left shoulder disability and need for treatment.  The City denied liability, and the matter came on for hearing before a compensation judge on January 3, 2013.  Evidence included the employee’s testimony and medical records and the reports of Dr. Salovich and Dr. Segal.  In a decision issued on January 28, 2013, the compensation judge concluded that the employee’s 1997 left shoulder injury was not a substantial contributing cause of the employee’s disability and need for treatment, and he therefore denied the contribution claim.  Kantor and its insurer appeal.

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).

[An equitable] apportionment can, of necessity, be based on no predetermined and precise formulas, but must be determined based upon the facts of each case.  Factors to be taken into consideration in reaching an apportionment decision include, but are not limited to, the nature and severity of the initial injury, the employee’s physical symptoms following the initial injury and up to the occurrence of the second injury, and the nature and severity of the second injury.

In the present case, Kantor and its insurer contend that substantial evidence does not support the compensation judge’s denial of their claim for reimbursement from the City based on the employee’s 1997 left shoulder injury.  Certainly there is evidence that supports their claim.  Specifically, the employee testified repeatedly that he was never symptom-free following the 1997 injury, that his symptoms flared up periodically after that injury, that he tried to use his right arm more for overhead work after that injury, and that he treated his condition with ibuprofen and ice, all before the March 2009 injury at Kantor.  In addition, Kantor’s claim is supported by the opinion of Dr. Segal, who concluded that the employee had likely sustained the labral tear in 1997, and, according to Dr. Segal, it was the labral tear that “was responsible for the majority of the surgery that was done.”  However, while the record might have supported a decision attributing some liability to the 1997 injury, we cannot conclude that the judge’s decision denying the reimbursement claim is unsupported by substantial evidence in the record as a whole.

Dr. Salovich concluded that the 1997 injury was merely a temporary strain of the trapezius musculature and “did not involve the acromioclavicular joint, rotator cuff, or glenoid labrum of the left shoulder.”  In explaining his conclusion, Dr. Salovich noted that Dr. Berlin’s 1997 evaluation of the employee, shortly after the work injury, was “not consistent with any type of permanent injury to the left shoulder occurring on November 26, 1997.”  As further support for his conclusion, Dr. Salovich noted that a 2009 MRI showed a tear of the rotator cuff “without evidence of significant retraction,” which, according to Dr. Salovich, was “consistent with a recent injury because an older injury would have caused retraction.”  The compensation judge expressly adopted the opinion of Dr. Salovich as most consistent with the evidence, especially the employee’s ability to continue full-time work as an electrician, as well as his work as a volunteer firefighter, for 11 years, with no treatment, after the 1997 injury.

On appeal, Kantor and its insurer argue in part that the judge’s adoption of the opinion of Dr. Salovich is inconsistent with the employee’s testimony about experiencing continuing symptoms after 1997, which the judge expressly found credible.  However, the judge addressed this issue in his memorandum, explaining as follows:

Dr. Berlin assessed the employee’s injury as a left shoulder sprain and indicated his belief that the injury would resolve.  While the employee reported that he had pain throughout the period between the assessments by Dr. Berlin and Dr. Phillipson, he was also engaged in overhead work as a journeyman electrician throughout the same period.  The compensation judge cannot determine to what extent, if any, the pain that the employee experienced between these appointments continued to be substantially attributable to the specific November 26, 1997 firefighting injury.

There are no radiological studies or scans during the intervening period demonstrating physiologic changes in the shoulder and no medical assessments to supplement the employee’s conclusion that the 1997 incident played a continuing role in the left shoulder symptoms.  The employee’s continued work as a firefighter and journeyman electrician throughout the intervening period and his engagement in overtime work as an electrician also make it difficult to assign ongoing effect to the 1997 injury.  The employee’s testimony reflects that the left shoulder symptoms were no longer constant after the initial four to six week period following the 1997 incident.  The symptoms came and went thereafter depending upon the employee’s activity level.  The employee estimated that he began to use ice and ibuprofen to relieve his pain in approximately 2000 and that he noticed disturbance of his sleep in approximately 2003.  The employee testified that his pain did not return to the level immediately following the 1997 incident and did not become constant again until after pulling wire at the Grand Portage job with Kantor Electric in late February of 2009.

We cannot say that the judge erred in his reasoning or his analysis of the evidence.  We therefore affirm the judge’s decision in its entirety.