This matter comes before the court on the appeal of West Bend Mutual Insurance; the insurer who was on the risk and liable for an admitted injury in 2005.  West Bend appeals the compensation judge’s decision apportioning liability for a 2012 injury and related medical treatment at 50% to the 2012 injury and 50% to the 2005 injury. The compensation judge’s February 3, 2015, apportionment order is in accord with Minnesota law, is supported by substantial evidence in the record, and is therefore affirmed.

The employee, Randolph Allee, began working for the employer, JN Johnson Sales and Service, in 1996 as a service technician.  The employer sells and installs commercial and industrial fire suppression systems.  In 2005, the employee was working for the employer as an installer and project manager.  On November 10, 2005, the employee sustained an admitted work injury when he was working on a ladder putting an 80-pound CO2 tank onto a suppression system.  As he leaned out with the tank, his body was in a twisted position with his arms stretched out.  He felt a pain in his low back which increased over the next week and began to radiate down the buttocks and into the left leg.

The employee was treated at the Cambridge Medical Center in December 2005 where he complained of left-sided low back pain with pain radiating into the left posterior thigh and leg.  An MRI scan performed on December 23, 2005, showed a moderate sized left-sided disc extrusion at L4-5 and a small left-sided protrusion at L5-S1.  The employee was referred to Dr. Daryll C. Dykes of the Minnesota Spine Center.  He was treated conservatively.  On January 18, 2007, the employee elected to undergo a left L4-5 hemilaminotomy and microdiscectomy for ongoing symptoms.  He was briefly off work following the surgery but was able to return to work thereafter without any formal restrictions.  The employee was rated with a 14 percent permanent partial disability.

The employee subsequently performed less and less installation work and more project manager work.  He testified that he asked co-workers to assist with the heavy work that he would previously have done himself.

In the summer of 2009, the employee returned to Dr. Dykes for a flare-up of his low back pain and a recurrence of pain in his buttocks and left leg since late April or early May.  He also had some right hip and thigh pain.  The employee reported his symptoms as “somewhat new” compared to his usual symptoms.  In July 2009, the employee complained of shooting pain into his right lower extremity.  An MRI scan on July 8, 2009, showed a right herniated nucleus pulposus at L3-4 with moderately severe stenosis.  There was a dorsal annular fissure at L5-S1 and an annular bulge at L4-5.  When Dr. Dykes saw the employee in August 2009, he told him that should his symptoms become more severe, an L4-5 fusion might be required.

On August 19, 2009, Dr. Dykes wrote a letter opinion in which he opined that the employee’s recent symptoms starting in April or May of 2009 were unrelated to the November, 2005 work injury.  He considered them likely related to a natural progression of degenerative disc disease.

For the next several years, the employee continued to perform his usual duties.  On May 10, 2012, the employee was working on a small installation job that he thought he could manage alone, when he sustained a second admitted injury to the low back.  While carrying an eight-foot fiberglass ladder, he experienced a sudden onset of severe low back pain which brought him to his knees.  He waited at the job site for a while until another employee was able to come to the site to complete the job, then returned to his family doctor at the Forest Lake Allina Clinic.

He resumed treatment with Dr. Dykes on May 18, 2012.  He reported radiating pain to the left leg and discomfort in the right thigh with occasional sharp radiating pain down the back of the leg into the calf and foot.  An MRI scan was performed on May 14, 2012.  The scan showed mild disc degeneration at L3-4 with a central and right paracentral annular tear.  There was disc degeneration at L4-5 with a moderately large central and left paracentral herniation with displacement and compression of the L5 nerve root.  Minimal annular bulging was present at L5-S1.  Comparison with the 2009 MRI showed resolution of the former L3-4 herniation.  The recurrent L4-5 herniation on the 2012 scan was a new finding.

In June 2012, due to the employee’s persistent back and leg symptoms, Dr. Dykes recommended either a decompression or fusion.  The employee was then seen by Dr. Richard Hadley for an independent medical examination.  Dr. Hadley opined that the May 10, 2012, work injury was a recurrent herniation at L4-5 which was a permanent aggravation to the employee’s pre-existing back condition.  He apportioned 50 percent of the employee’s condition to the 2012 injury and 50 percent to the 2005 work injury.  He recommended a decompression and fusion at L4-5.

The employee underwent a three-level decompression and fusion on December 26, 2012.  He was unable to return to work until April 2013, when he returned with work restrictions.  As of the date of hearing, the employee was working as a project manager for the employer.  In this job, he continues to do some lighter installation work but limits the extent of his physical labor.

In a narrative report dated September 14, 2014, Dr. Dykes diagnosed the 2012 injury as an acute recurrent disc herniation at L4-5 related to the employee’s work activities.  He opined that the 2005 work injury was not a substantial contributing factor to this injury or to any condition or treatment after November 7, 2007.  He apportioned the employee’s condition following the 2012 injury, and the need for the fusion surgery, at 1/3 due to the 2012 work injury and 2/3 to a naturally occurring degenerative condition.  He attributed zero apportionment to the 2005 injury.

West Bend Mutual Insurance was on the risk in 2005 and Western National Insurance was on the risk for the 2012 injury.  The matter came on for hearing before a compensation judge solely on the issue of apportionment.  The compensation judge apportioned liability for the 2012 injury and associated medical treatment at 50 percent to the 2012 injury and 50 percent to the 2005 work injury.  The employer and insurer West Bend Mutual appeal the compensation judge’s apportionment determination.

In reviewing cases 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.  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, “[f]actfindings are clearly erroneous only if the reviewing court on the entire evidence is left with a definite and firm conviction that a mistake has been committed.”  Northern States Power Co. v. Lyon Foods Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).  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 the evidence or not reasonably supported by the evidence as a whole.”  Id.

The compensation judge found that the 2005 work injury was a substantial contributing cause to the employee’s medical condition following the 2012 work injury.  The judge apportioned liability for ongoing disability and treatment at 50% to each injury.  Appellants, employer and West Bend, argue on appeal that substantial evidence fails to support the compensation judge’s apportionment opinion.  They contend that the evidence establishes that the employee fully recovered from the 2005 work injury and that the 2012 work injury was an entirely separate new injury and condition.

Equitable apportionment is not a finding based on a precise formula but rather is based on all the facts and circumstances of a case.  Factors considered in determining apportionment include the nature and severity of the initial injury, the employee’s physical symptoms following the initial injury and before the second injury, the nature and severity of the second injury, and the period of time between the injuries.  Goetz v. Bulk Commodity Carriers, 303 Minn. 197, 226 N.W.2d 888, 27 W.C.D. 797 (1975); Harvala v. Noeske Lumber, 44 W.C.D. 118, 126 (W.C.C.A. 1990).

The appellants contend that, viewed solely in the light of the Goetz factors, the evidence does not support the judge’s apportionment of any part of the liability for the employee’s treatment and disability following the 2012 injury onto the 2005 injury.  Specifically, they argue that both the nature and severity of the initial injury, and the symptoms following that injury, were minimal.  They point out that in 2005 the employee had a slow onset of pain, was able to wait to seek medical care, and could manage his symptoms up to the date of surgery, after which he was largely symptom free and had no work restrictions.  Subsequently, the employee had minimal pain and needed no significant further treatment for several years.  They further point out that, in contrast, the employee’s 2012 injury caused immediate severe pain, prompted immediate medical treatment, led to a fusion surgery, and resulted in permanent work restrictions.

Considering the entire record of this case, there is also evidence, under the Goetz factors, that supports the judge’s decision to apportion liability between the 2005 and 2012 injuries.  Although the employee was able to work without formal restrictions following the initial injury, he testified that his doctor advised him to be cautious of his activities, and that he subsequently limited the amount of heavy work he performed in his job, requesting assistance from co-workers instead.  Moreover, the 2005 injury was not insignificant.  The injury required surgery resulting in a permanent partial disability of 14 percent.  Finally, although the 2012 injury came on with a more severe and immediate effect than did the 2005 injury, it involved a recurrent disc herniation at the same level as the 2005 injury.  A determination that the 2005 work injury was a contributing cause of the 2012 injury is consistent with these facts.  Accordingly, we do not accept the argument that the evidence bearing on the Goetz factors compels the conclusion that the employee’s injuries were wholly unrelated.

The appellants next argue that the compensation judge improperly relied on “a dubious collection” of additional factors not specifically set out in Goetz and which, they contend, were “arbitrary, misleading and unsupported by case precedent.”  They assert that consideration of these factors renders the judge’s determination clearly erroneous.  The factors which they contend fall into this category include a consideration of the mechanisms of injury, of the extent of medical treatment received or recommended following each injury, of the permanency associated with each injury, of the employee’s work restrictions, and of the effects of each injury on the employee’s activities.

We do not view these so much as additional factors but as simply more detailed aspects of the evidence bearing on some of the Goetz factors.   Consideration of the nature and severity of an injury reasonably involves consideration of the mechanism of the injury, its associated treatment, any resulting permanency, and the effects of the injury both at the employee’s job as well as in daily activities.  Moreover, we note that our decision in Goetz expressly made clear that the factors proposed there were not intended to be exclusive.  Thus, we do not agree that the judge’s analysis of the factors the appellants have denoted as “additional” constitute reversible error.  These factors were appropriate to the judge’s apportionment determination, and the relative weight given to each was a matter entrusted to the compensation judge as the trier of fact.

The judge also relied on the expert medical opinion of Dr. Hadley, which he accepted over that of Dr. Dykes.  Dr. Hadley opined that 50 percent of the employee’s current condition was attributable to each of the two work-related injuries.  As a general rule, where there is adequate foundation for the opinions adopted by the judge, this court will normally uphold the compensation judge’s choice among medical experts.  See Nord v. City of Cook, 360 N.W.2d 337, 342-43, 37 W.C.D. 364, 372-73 (Minn. 1985).

The appellants argue that the judge should not have accepted Dr. Hadley’s apportionment opinion, asserting that Dr. Hadley’s opinion lacked foundation in that he did not specifically list all the medical records he reviewed.  First, we note that the appellants did not offer any foundational objection to Dr. Hadley’s report at the hearing below.  Next, we note that Dr. Hadley’s report states that, as part of his examination, the “available records were reviewed.”  Dr. Hadley took a history from the employee, examined the employee, and reviewed relevant medical records and tests.  This level of knowledge supports an adequate foundation for a doctor to render an expert medical opinion.  Drews v. Kohl’s, 55 W.C.D. 33 (W.C.C.A. 1996); see also Grunst v. Immanuel-St. Joseph Hosp., 424 N.W.2d 66, 68, 40 W.C.D. 1130. 1132-33 (Minn. 1988).  Finally, even if we were to assume that Dr. Hadley did not have access to all of the prior medical records, certain facts may be unknown to a doctor without damaging foundation for the medical opinion as long as the omissions do not mislead the fact-finder.  See Scott v. Southview Chevrolet Co., 267 N.W.2d 185, 188, 30 W.C.D. 426, 431 (Minn. 1978).  The appellants did not offer any facts to support that the fact-finder was misled.

The appellants also argue that Dr. Dyke’s opinion was entitled to greater weight than that of Dr. Hadley because Dr. Dyke was a treating physician.  As we noted above, the weighing of the evidence is a matter delegated to the compensation judge.  The question of whether the treating physician’s opinion was entitled to greater weight was one which fell within the discretion of the judge and she was not persuaded.

Finally, the appellants contend that the compensation judge erred in failing to make any findings as to whether the employee had a preexisting low back condition.  The sole issue before the judge was one of equitable apportionment between the two work-related injuries.  There were no medical records in evidence predating the 2005 work injury which showed any significant low back problems.  We decline to view the absence of findings about a hypothetical pre-existing condition in the present case as constituting reversible error.

Substantial evidence of record supports the compensation judge’s findings on apportionment and we affirm.