The employer and Western National Mutual Insurance Company appeal from the compensation judge’s finding that Western National Mutual Insurance Company is solely liable for the employee’s disability during periods at issue from and after April 10, 2008, and from the judge’s award of wage replacement and other compensation for such disability.  We reverse in part the judge’s award of temporary partial disability benefits, and we affirm on all other issues.

On November 5, 1991, Jeffrey Jacobson [the employee] sustained an injury to his low back while lifting a transmission evidently weighing over two hundred pounds from the back of a pick-up truck to the ground, in the course of his work as a service runner with Suburban Chevrolet [the employer].  The employee’s job as a service runner normally entailed picking up parts weighing up to seventy pounds and delivering them to mechanics in the service department.  The employee was twenty-two years old on the date of his injury and was earning a weekly wage of $266.40.  At the time of his injury, the employee evidently had immediate shooting pains in his low back, and about a week later, on November 13, 1991, he sought treatment for the injury at Camden Physicians, where he complained of constant low back pain for the past two weeks, predominantly on the right side, with radiation down into his foot.  He was restricted from all work for five days, and on November 19, 1991, he followed up with his family doctor, Dr. Glenn Schiffler.  Dr. Schiffler suspected a herniated lumbar disc, but, noting the employee’s normal neurologic exam, he refilled the employee’s medication and released him to work with no heavy lifting, anticipating a possible need for a CT scan if the employee did not make significant progress.

The employee’s right leg pain continued, and on December 20, 1991, he returned to Camden Physicians, and a CT scan was ordered.  The scan was conducted on December 23, 1991, and was read to reveal a large central and right-side extruded disc herniation at L5-S1 that was severely compressing the right side of the thecal sac and the right S1 nerve root.  When the employee was showing no improvement by January 2, 1992, Dr. Schiffler referred the employee to orthopedic surgeon Dr. Paul Crowe, who apparently prescribed physical therapy.  When he saw the employee again on February 6, 1992, and noting that physical therapy had not relieved the employee’s symptoms, Dr. Crowe recommended surgery, and on February 10, 1992, he performed a laminotomy and excision of the herniated disc at what is variously identified in the medical records as L5-6 and L4-5 of the employee’s spine.  The employee appeared to achieve a good result with his surgery, and on May 11, 1992, Dr. Crowe released him on a return-as-needed [PRN] basis to return to his job with the employer without restrictions, with the understanding that he should seek some help if he was going to be lifting anything heavier than fifty pounds or anything particularly awkward or cumbersome.  The employer and its insurer at the time of the injury, Western National Mutual Insurance Company [Western National], acknowledged liability for the injury and paid benefits that ultimately included $6,750.00 in compensation for a 9% permanent partial disability of the whole body.

For about four years after his release to return to work, the employee was evidently able to participate in normal everyday work and recreational activities, including golfing, apparently with only an occasional temporary flare-up in his low back symptoms.  On July 28, 1996, he sustained a second injury to his low back, this while lifting a pickup truck box’s side panel evidently weighting between 100 and 120 pounds.  The injury occurred in the course of his work either as a service runner or as a parts runner for the employer, a job typically entailing pulling parts, still normally weighing up to seventy pounds, from inventory and delivering them to shops around town.  The injury resulted in sharp and constant low back pain that radiated upward when he walked, that was aggravated by bending over, and that also radiated down the front of his right leg, with numbness and paresthesias diffusely down through his right foot.  No diagnostic scans were performed, the injury was diagnosed as an acute lumbar strain, and the employee was restricted from working until August 27, 1996, when he was released to return to work restricted from lifting over first twenty and then thirty pounds.  Upon examination of the employee on October 16, 1996, Dr. Crowe noted no residual problems, negative findings on straight leg-raising tests, and normal motor power in the right leg, and he released the employee on a PRN basis to return to his job with the employer on October 18, 1996, without restrictions.  On November 26, 1996, Dr. Crowe evidently completed a Healthcare Provider Report, in which he opined that the employee had reached maximum medical improvement [MMI] with regard to his July 1996 work injury as of October 16, 1996, having sustained no permanent partial disability.^[1]  At the time of this second injury, the employee was twenty-seven years old and was earning a weekly wage of $313.41.  The employer and its workers’ compensation insurer at the time, MADA Insurance Exchange, with claims administered by Berkley Risk Administrators Company, LLC [Berkley Risk], acknowledged liability for the injury and paid about two weeks of temporary total disability benefit and various medical expenses.

On August 29, 1997, the employee sustained yet a third injury to his low back, this while again lifting a transmission in the course of his work as either a service or a parts runner for the employer, work still normally entailing lifts up to only seventy pounds.  On September 2, 1997, he saw Dr. Crowe again, to whom he complained of an immediate onset of significant left leg pain following the injury.  Upon examination he had a positive straight leg finding on the left, and Dr. Crowe restricted him from working.  He was no better on September 8, 1997, with continued radicular left leg pain, but by September 16, 1997, his pain was resolving, and Dr. Crowe released him to work on a PRN basis, restricted from lifting over sixty pounds.  At the time of this third injury, the employee was twenty-eight years old and was earning a weekly wage of $459.00.  The employer and its workers’ compensation insurer at the time, Michigan Physicians Mutual Liability Company, with claims administered by ASU Risk Management Services, Ltd. [ASU Risk], acknowledged liability for the injury and paid about two weeks of temporary total disability benefits, together with various medical expenses.

Upon follow-up examination of the employee at Occupational Medical Consultants on September 24, 1997, Dr. Allen Jakubowski reported that the employee was being seen with regard to a left-side lumbar radiculopathy at L4-5 that he had sustained working for the employer on August 29, 1997.  Dr. Jakubowski noted that on that date the employee no longer had any radiation of pain down his left leg and that the employee’s back felt more or less one hundred percent better, although the employee did report some residual tightness after performing his job with a forty-five pound lifting restriction.  Upon examination findings that included full range of motion in the low back without any residual pain or stiffness, Dr. Jakubowski released the employee to return to regular duty with the employer on September 25, 1997.  On November 7, 1997, Dr. Crowe completed a Healthcare Provider Report on which he certified that the employee had reached MMI with regard to his injury as of that date, having sustained no related permanent partial disability.

Between 1998 and 2005, the employee began to experience flare-ups of low back pain and lower extremity pain that were similar in nature and location to symptoms that he had experienced at the time of his 1991 injury.  On July 28, 2005, the employee was seen again at Camden Physicians, with complaints of low back pain that had come on in the past two days without any apparent injury.  Physical examination revealed almost no range of motion, with pain upon any attempt, and, although his walking and reflexes were normal, the examining doctor diagnosed acute lumbar strain with distant postoperative disc status and prescribed medication.  Dr. Crowe examined the employee again on August 9, 2005, and, finding the employee’s back range of motion now “probably half normal,” he diagnosed acute lumbar strain, prescribed Vicodin, Flexeril, and physical therapy, and instructed the employee to follow up by phone in three weeks, by which time the doctor “expect[ed] complete recovery.”  When he saw the employee again on September 27, 2005, Dr. Crowe noted that the employee’s lumbar strain was “now resolved,” and he released the employee on a PRN basis.  However, about three weeks later, on October 21, 2005, the employee sought treatment again for his low back, complaining to Dr. Schiffler that he had been picking up a bag of grass three days earlier when he felt pain in his low back that radiated down his right leg to his calf and into his foot.  Dr. Schiffler diagnosed low back pain with right calf radicular symptoms and prescribed additional Vicodin.

The employee returned to Dr. Schiffler for further treatment on December 6, 2005, complaining that, on about December 1, 2005, he had had pain again on the right side of his low back, with radicular symptoms into his right lower extremity.  At the time of the onset of his pain, the employee had evidently been working as a parts counterman for the employer, a position that apparently continued to entail the handling of parts from inventory weighing up to seventy pounds but also entailed taking telephone orders for such parts, looking up those parts on a computer, and billing out parts delivered.  Dr. Schiffler diagnosed right lumbar pain with right lower extremity radicular symptoms, which he related to the employee’s previous surgery by Dr. Crowe in February 1992, and he ordered an MRI scan and prescribed prednisone.  The scan was performed on December 7, 2005, and was read to reveal status post right laminectomy and facetectomy at L4, mild spinal stenosis at L4 caused by a bulging disc superimposed on hypertrophic changes on the left facets, which also caused severe left lateral recess stenosis at L4, and left neural foraminal stenosis at L5-S1.  On December 1, 2005, the employee had been thirty-six years old and had been earning a weekly wage of $711.41, and the employer was insured against workers’ compensation liability by Farm Bureau Mutual Group [Farm Bureau].

Subsequent to the flare-up in his symptoms in 2005, the employee tried without success to reduce his low back and lower extremity symptoms through conservative care, including medications, epidural injections, and a back brace.  On April 4, 2006, noting that nothing had helped to relieve the employee’s symptoms, Dr. Crowe concluded that the employee was a candidate for decompression and instrumented spinal fusion, but the employee wanted first to investigate the possibility of total disc replacement.  Dr. Crowe referred him for a consultation in that regard, but the employee was found not a candidate, due to a multilevel facet arthrosis condition.  On May 7, 2006, the employee was seen at Maple Grove Urgent Care complaining of recurrent lower back pain and muscle tightness that was now radiating into both lower extremities to below the knees, which had come on four days earlier, after no known injury.  On August 23, 2006, the employee again sought emergency treatment for low back pain, after golfing and sleeping on a mattress on the floor over the weekend.  Upon examination by Dr. Crowe on September 12, 2006, the employee was reporting feeling dramatically better, but on November 21, 2006, having not required any pain medication for over two months, he sought further treatment again after developing a spasm in the left side of his low back while installing an infant seat in his car.

The employee’s treatment for low back and bilateral leg complaints continued into the following year.  On January 8, 2007, on referral from Dr. Crowe, he was evaluated by Dr. Donald Asmussen at Physicians Neck and Back Clinics, to whom the employee reported that his symptoms dated to December of 2005.  On February 7, 2007, the employee received emergency treatment for sharp back pain that radiated down his right leg, after twisting to pick up his three-year-old daughter the night before.  He was seen again on an emergency basis on February 24, 2007, with complaints of shooting bilateral leg pain over the past three days, without any history of trauma.  When he was examined by Dr. Crowe again about two weeks later, on March 6, 2007, Dr. Crowe concluded again that the employee may be a candidate for a decompression and instrumented spinal fusion at L4-5, and he ordered an MRI scan.  The employee’s pain grew progressively worse in April, and on April 24, 2007, Dr. Crowe restricted him from all work.

The MRI scan was conducted on May 4, 2007, and was read to reveal post-operative changes consistent with an L5 laminectomy, moderate canal stenosis at L4-5 due to a minimal posterior osteophytic ridge and a broad-based disc bulge, and a hypertrophic osteophyte of the left L4-5 facet that narrowed the lateral recess and impinged on the traversing left L5 nerve root.  On May 15, 2007, Dr. Crowe noted that the most problematic level, which was “highly degenerative with stenosis and bulging,” was “an old operative level.”  On June 7, 2007, subsequent to further emergency treatment of the employee on May 28, 2007, Dr. Crowe opined in a letter replying to a telephone query of the employee as follows:

On June 18, 2007, the employee filed a claim petition, alleging his entitlement to wage replacement benefits continuing from March 25, 2007, undetermined permanent partial disability benefits, and medical benefits including approval of the proposed decompression and fusion surgery.  On July 17, 2007, at the employee’s request, Dr. Crowe formally agreed to perform a revision decompression fusion at L4-5 and L5-S1 of the employee’s spine.

On September 21, 2007, the employee was examined for Western National by neurosurgeon Dr. Terry Hood.  In his report on that date, Dr. Hood diagnosed discogenic pain syndrome emanating primarily from the L4-5 level of the employee’s spine, with lesser degenerative disc disease at the two adjacent levels.  Dr. Hood opined in part that the employee’s 1991, 1996, and 1997 work injuries and his alleged 2005 work injury were all substantial contributing factors in the employee’s current low back condition.  Dr. Hood apportioned 40% liability to the 1991 injury, 20% each to the 1996 and 1997 injuries, and 20% to the alleged 2005 injury, concluding that the fusion surgery recommended by Dr. Crowe would be reasonable and necessary for the relief of the employee’s work-injury-related pain.

On November 13, 2007, Western National petitioned for a temporary order, permitting payment of wage loss benefits, rehabilitation benefits, and medical expenses associated with the surgical procedure recommended by Dr. Crowe, pending a final determination of liability.  The requested temporary order was served and filed on November 29, 2007.  Under that order, Western National agreed to pay, pending a determination of liability, all medical expenses associated with the employee’s imminent surgery, together with fourteen weeks of subsequent temporary total disability benefits and rehabilitation expenses.  Eventually, on December 21, 2007, Western National paid $5,093.60 in temporary total disability benefits and $1,523.40 in attorney fees pursuant to that order.

The employee’s surgery was performed on January 2, 2008 - - a revision and decompression of recurrent spinal stenosis at L4-5, together with fusion at that same level employing a Capstone interbody fusion device and Legacy pedicle screws.  The decompression included a complete facetectomy on the right and a partial facetectomy on the left.  On March 3, 2008, in reply to a letter from the employee’s attorney, Dr. Crowe opined, contradicting in part his June 7, 2007, letter to the employee, that all three of the employee’s specific work injuries as well as a Gillette^[2]-type injury on December 1, 2005, were significant injuries all substantially contributing to the employee’s current diagnosis of degenerative disc disease with discogenic pain syndrome at L4-5.  He apportioned twenty-five percent liability to each of the four, adding that Dr. Hood’s apportionment of forty percent to the 1991 injury and twenty percent to each of the other three would also be acceptable.

On March 4, 2008, the employee filed an amended claim petition, alleging entitlement to payment of an additional $4,515.00 under the temporary order and naming July 28, 1996, August 21, 1997, and December 1, 2005, as dates of injury in addition to November 5, 1991.  On March 5, 2008, Western National made payment of $3,528.00.  On April 7, 2008, the employee was released to return to work with restrictions on April 16, 2008.  Meanwhile, he was temporarily totally disabled from April 10, 2008, through April 15, 2008, while he healed from his surgery.  He returned to work at his job with the employer on April 16, 2008, restricted for three weeks from lifting over fifteen pounds and from working more than four hours a day, and on May 13, 2008, he apparently returned to full-time work at his regular duties.

On May 19, 2008, in reply to queries of the employee’s attorney, Dr. Crowe issued a letter in which he diagnosed the employee’s current condition as “degenerative disc disease with a discogenic pain syndrome at L4-5” and now opined that the employee’s work injuries of 1991, 1996, and 1997 and his alleged work injury of 2005 were all substantial contributing factors in that condition.  He indicated further that he would apportion either 25% liability to each of those four events or, as did Dr. Hood, 40% to the 1991 injury and 20% to each of the other three events.

On July 21, 2008, the employee was examined for Berkley Risk by neurologist Dr. Daniel Randa.  In his report on that date, Dr. Randa concluded that the employee’s November 1991 work injury was the sole substantial cause of the employee’s current low back condition and need for fusion surgery in January of 2008.  He concluded that the employee’s flare-ups since then appeared all to be temporary aggravations of a pre-existing condition.  It was his opinion that the progressive increase in the employee’s pain in December of 2005 reflected only an anticipated consequence of the February 1992 lumbar laminectomy and discectomy related to the initial 1991 injury.  It was his opinion, therefore, that the 1991 injury was the principal cause not only of the employee’s pain in December 2005 but also of his need for the L4-5 fusion in January 2008.  Dr. Randa apportioned no liability to any injury other than the 1991 injury.

On October 16, 2008, Western National filed a petition for contribution and/or reimbursement from Berkley Risk, ASU Risk, and/or Farm Bureau, for seventy-five percent of the benefits that it had paid under the temporary order.

On November 17, 2008, the employee was examined for ASU Risk by orthopedic surgeon Dr. Stephen Barron.  In his report on November 18, 2008, Dr. Barron concluded in part that the employee’s specific work injury on November 5, 1991, and a Gillette-type injury of the employee on December 1, 2005, were substantial contributing factors in the employee’s current low back condition and need for medical treatment and that his 1996 and 1997 work injuries were temporary and were not substantial contributing factors.  Dr. Barron apportioned 60% liability for that condition and that need to the 1991 injury and 40% liability to the alleged 2005 Gillette-type injury.

On November 26, 2008, the employee was examined for Farm Bureau by orthopedic surgeon Dr. Richard Strand.  In his report on that date, Dr. Strand concluded in part that there was no evidence of a Gillette-type injury culminating on December 1, 2005, and that the employee’s treatment at Camden Physicians in October 2005 was unrelated to any work activity.  He indicated that his finding of no injury on December 1, 2005, was based on his conclusion “that there was no specific date that could be anywhere related to December 1, 2005,” and his conclusion “that [the employee’s] work as a parts desk person is not a sort of activity, which would cause degeneration in the spine.”  He noted further that degeneration in a vertebral disc space that had previously been operated on, such as that present in the employee’s spine, would be a natural expectation of someone, like the employee, who is six-feet-three-inches tall and significantly overweight.

On April 2, 2009, Dr. Hood testified by deposition, in part that, when he saw the employee in September 2007, he had felt that “there was an event and a decided change in his condition, and it seemed to be a permanent change in that his symptoms began then [in December of 2005] and by the time I had seen him had been continuous to that point in time.”  After being presented by Western National’s attorney with a nine-page factual hypothetical to which many objections were raised by the attorney for Farm Bureau, Dr. Hood testified as follows as to whether or not the employee suffered a Gillette-type injury on or about December 1, 2005:

On April 20, 2009, Dr. Strand wrote to the attorney for Farm Bureau, indicating that he had now reviewed various additional medical records, including Dr. Hood’s deposition of April 2, 2009, and the report of Dr. Barron dated November 18, 2008.  Dr. Strand indicated that he had then compared these with his own previous report and the report of Dr. Randa’s independent medical examination and was still “in agreement with Dr. Randa that the substantial contributing factor [in the employee’s] condition is not an alleged Gillette injury, nor a specific injury in 2005, but rather his initial injury in 1991.”  On April 21, 2009, having reviewed the reports of Drs. Barron and Strand and the deposition testimony of Dr. Hood, Dr. Randa essentially reiterated in deposition testimony the opinions that he had expressed in his report on July 21, 2008.

The employee’s claim petition and Western National’s petition for contribution and/or reimbursement were consolidated and came on for hearing on April 23, 2009.  Issues at hearing were as follows:  (1) whether the employee was entitled to temporary total disability benefits from April 10, 2008, through April 15, 2008; (2) whether the employee was entitled to temporary partial disability benefits from April 16, 2008, through May 14, 2008; (3) whether the employee was entitled to a whole-body permanent partial disability rating in excess of the 9% for which he had already been compensated; (4) whether the employee was entitled to an additional award as a penalty, pursuant to Minnesota Statutes section 176.225; (5) whether the employee sustained a Gillette-type personal injury to his low back culminating on December 1, 2005, arising out of and in the course of his employment with the employer; (6) the nature of the employee’s work injury on July 28, 1996; (7) the nature of the employee’s work injury on August 29, 1997; (8) whether Western National was entitled to contribution and/or reimbursement for benefits paid; (9) whether any liability should be equitably apportioned; and (10) who should be the paying agent for any benefits due.  At the hearing, the employee testified in part that he did not recall the incident of his second work injury, on July 28, 1996, or any treatment or symptoms that he had as a result, only that those symptoms eventually resolved.  Nor did he recall the incident, treatment, or subsequent symptoms of his third work injury, on August 29, 1997, except that those symptoms, too, eventually resolved.  He testified further that his low back symptoms in late 2005 came on but did not go away prior to his eventual fusion surgery, that there was no specific incident at work or away from work to which they seemed related, and that he could not recall any activities at work that had caused his symptoms.

By findings and order filed June 19, 2009, the compensation judge concluded in part that he could not decide the permanent partial disability issue because “[t]he parties and the medical providers have not stated claims, opinions, or positions concerning permanent partial disability of the whole body using the appropriate permanent partial disability schedules,” and “[d]etermining permanent partial disability of the whole body without allowing the parties to adequately present their positions, claims, and defenses would be to deny them due process.”  On that conclusion the judge dismissed without prejudice the employee’s claim for additional permanent partial disability benefits, indicating that the employee remained free to file an appropriate pleading in the future.  There has been no appeal from this conclusion regarding the employee’s claim for permanent partial disability benefits.

With regard to other matters at issue, the judge found that the employee’s work injury on July 28, 1996, was a temporary aggravation of the employee’s pre-existing low back condition that resolved no later than October 16, 1996.  The judge indicated that he based this conclusion on the employee’s own testimony, medical records in evidence, and the opinions of Dr. Randa, Dr. Barron, and Dr. Strand.  The judge found also that the employee’s work injury on August 29, 1997, was also a temporary aggravation of a pre-existing condition, which resolved no later than November 7, 1997, on which date, the judge concluded, the employee attained MMI with no permanent partial disability.  The judge indicated that he based his conclusion that the 1997 work injury was temporary also on the employee’s own testimony, medical records in evidence, and the opinions of Drs. Randa, Barron, and Strand.  The judge found that, upon his return to work on April 16, 2008, the employee was temporarily partially disabled through May 14, 2008, having not been released to return to full-time work until May 12, 2008.  Based on the opinion of Dr. Strand, which he expressly found to be of adequate foundation, and expressly finding the opinions of Dr. Crowe, Dr. Hood, and Dr. Barron unpersuasive, the judge concluded that the employee had not sustained a Gillette-type injury on December 1, 2005, that Western National had failed to establish entitlement to contribution and/or reimbursement for any benefits that it had paid, and that it had been established by a preponderance of the evidence that the November 5, 1991, work injury was a substantial contributing factor in the employee’s low back flare-up in December 2005 and in his subsequent resulting disability and need for medical treatment.  Further, the judge found that Western National’s payment of benefits under its temporary order was late without explanation and so unreasonable.

Based on those findings, the compensation judge denied Western National’s claim for reimbursement and/or contribution, and he ordered it to pay the employee’s claim for temporary total and temporary partial disability benefits, a penalty in the amount of $675.00, partial reimbursement of statutory attorney fees pursuant to Minnesota Statutes section 176.081, subdivision 7, the employee’s reasonable costs and disbursements, and statutory interest on benefits awarded.  The employer and Western National appeal from the judge’s award of temporary partial disability benefits, from the judge’s conclusion that the employee did not sustain a Gillette-type injury on December 1, 2005, from the judge’s decision not to equitably apportion the liability at issue among the employee’s various admitted work injuries, and from the judge’s failure to explain in a more detailed memorandum his reliance on the medical opinion that he accepted.

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. Lyion 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.

At Finding 1, the compensation judge concluded in part, based on stipulation of the parties, that the employee’s average weekly wage on the date of his November 1991 work injury was $266.40.  Petitioner’s Exhibit 14, offered and received into evidence without objection, indicates that the employee’s gross earnings during each of the five weeks of his temporary partial disability claim ending April 16, April 23, April 30, May 7, and May 14, 2008, were, respectively, $83.43, $385.16, $405.47, $411.34, and $645.52.  At Finding 44, the compensation judge concluded that the employee was temporarily partially disabled from April 16, 2008, through May 14, 2008, subsequent to his January 2008 fusion surgery, and at Order 2 the judge awarded compensation for the full period of that disability.  Minnesota Statutes section 176.101, subdivision 2.(b), provides in part that “[t]emporary partial [disability] compensation may be paid only while the employee is employed, earning less than the employee’s weekly wage at the time of the injury.”  Minn. Stat. § 176.101, subd. 2.(b) (underscoring added).  The employer and Western National contend first, aside from issues of liability and apportionment, that the compensation judge’s award of temporary partial disability benefits is erroneous as a matter of law, in that the employee’s demonstrated wage during all but one week of the benefits period at issue exceeded his stipulated weekly wage at the time of his 1991 work injury - - the only injury that the judge found causally related to the employee’s ongoing back problems after resolution of his 1997 injury.  We agree.  Therefore we reverse the judge’s award of temporary partial disability benefits for those four weeks during which the employee earned more at his post-injury job than he earned at his date-of-injury job.

The compensation judge concluded at Findings 47, 48, and 49, in express reliance on the opinion of Dr. Strand and in express rejection of the opinions of Drs. Crowe, Hood, and Barron, that it had not been established that the employee sustained a Gillette-type injury to his low back culminating on December 1, 2005, in the course of his work for the employer.  Western National contends that that conclusion of the judge is both contrary to Minnesota workers’ compensation law and unsupported by substantial evidence.  It argues that that the conclusion is contrary to law in that the medical opinion of Dr. Strand on which it relies attaches, contrary to the mandates of Steffen v. Target Stores, significant weight to the employee’s own lack of recollection regarding work causation of his injuries, instead of focusing more solely on evidence of the employee’s job tasks over time.  See Steffen v. Target Stores, 517 N.W.2d 579, 581, 50 W.C.D. 464, 467 (Minn. 1994) (“[w]hile that kind of evidence [evidence that specific work activity caused specific symptoms] may be helpful as a practical matter, . . . the question of a Gillette injury primarily depends on medical evidence”).  Moreover, Western National argues, it was legally inappropriate for Dr. Strand, without lawyer’s credentials, to place any emphasis at all on the legally complex issue of the date of the alleged Gillette injury, rather than focusing solely on the potential of causation by the work activities.  On factual grounds, Western National argues that the judge’s conclusion is unsupported by substantial evidence in that it relied on a medical opinion that was not only contrary to the opinions of five other medical experts but also, contrary to the requirements of Nord v. City of Cook, based on factual premises that were themselves unsupported by substantial evidence.  See Nord v. City of Cook, 360 N.W.2d 337, 342-43, 37 W.C.D. 364, 372-73 (Minn. 1985) ("the trier of fact's choice between experts whose testimony conflicts is usually upheld [unless] the facts assumed by the expert in rendering his opinion are not supported by the evidence").  It argues that Dr. Strand’s opinion, contrary to the opinions of at least three other opining doctors, was based on a false presumption as to the nature of the employee’s job duties.  We are not persuaded

In its brief, Western National argues that “it appears that the compensation judge utilized the pre-Steffen standard, as he attached significant weight to the employee’s lack of memory recall, regarding the causation of his injuries.”  Western National does not cite any particular evidence in the statements of Dr. Strand to support this inference, either in his “Discussion” of the issues or elsewhere in his report, nor do we find any such evidence.  It is true that Dr. Strand expressly bases his conclusion on an opinion “that there was no specific date that could be anywhere related to December 1, 2005.”  While we understand the appellant’s argument that medical expertise does not qualify one to offer a professional opinion on the complex legal issue of the date of a Gillette-type injury, we are not persuaded, having scrutinized the whole of Dr. Strand’s report, that it was the specific date of any injury that concerned the doctor so much as it was the specific occurrence of any new injury.  Our sense of Dr. Strand’s opinion is that he saw the employee’s post-2005 problems merely as continuing consequences of the employee’s February 1992 surgery in light of the employee’s ongoing degenerative disc disease, as had Dr. Randa, with whom Dr. Strand expressly agreed.  We will not reverse the judge’s conclusion on this issue on grounds that Dr. Strand’s opinion was legally improper.

With regard to Western National’s arguments on factual grounds, we would note initially that we find nothing in the law precluding a compensation judge’s reliance on a medical opinion that is contrary to a majority of other medical opinions.  We acknowledge that the weight of the evidence may be affected by the size of such a disparity, but Dr. Strand’s opinions are voiced in the context of two very objective reports, one very thorough and detailed, and we cannot conclude that the judge’s decision to rely on those opinions was unreasonable.  With regard to the issue of Dr. Strand’s relative awareness of the employee’s work as a counterman for the employer, we can only note that Dr. Strand’s awareness of such information and his foundation for an opinion on this issue cannot be said to be materially any different from that of most of the experts here with contrary opinions.  Dr. Strand indicated that, in addition to his personal interview of the employee on November 26, 2008, he had read and reviewed a substantial portion of the employee’s medical records.  These included not only records at Camden Physicians and Physicians Neck & Back and records of Dr. Schiffler and Dr. Crowe and Dr. Sherman but also the independent medical examination reports of Dr. Barron and Dr. Randa and Dr. Hood, together with the deposition testimony of the latter, which contained a nine-page factual hypothetical developed by Western National’s own attorney.  We cannot conclude that Dr. Strand’s foundation for an opinion on this issue was any more or less deficient than was the foundation for any other expert’s opinion on this issue.  That Dr. Strand may have come to a different conclusion was his professional prerogative, as was the judge’s decision to rely on that conclusion.  See Nord, 360 N.W.2d at 342-43, 37 W.C.D. at 372-73.

Nor do we understand, from the doctor’s statement that the employee’s work as a counterman was “not a sort of activity, which would cause degeneration in the spine,” that Dr. Strand misunderstood the stresses of that position.  It is evident from a scrutiny of the employee’s testimony at hearing that the physical aspects of his work for the employer, always normally limited to about seventy pounds lifting, changed little over the course of his total employment.  That work, within those normal limits, had never caused a Gillette-type injury, and the employee’s doctors had apparently felt confident in repeatedly releasing him to work within those limits.  The only injuries that the employee had sustained over the course of his fifteen years working for the employer were specific injuries, when the employee was lifting substantially more than what was normal for him on his job.  Absent any particular event precipitated by the employee’s lifting more than what was normal in his work, it was not unreasonable for Dr. Strand to conclude that the employee was not subject to a minute-trauma injury that his own treating doctors had not particularly foreseen in the normal course of his work.  Because Dr. Strand’s opinion was not unreasonable, and because the compensation judge’s conclusion in reliance on that opinion was also therefore not unreasonable, we affirm the judge’s conclusion that a Gillette-type injury on December 1, 2005, was not proven.  See Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.

In express reliance on the opinions of Drs. Randa, Barron, and Strand, the compensation judge concluded at Findings 18, 23, and 24 that the employee’s July 1996 and August 1997 work injuries were temporary injuries that quickly resolved without related permanent partial disability, and he concluded at Finding 48, as indicated above, that the employee sustained no work-related injury at all on December 1, 2005, as alleged.  On these findings, the judge concluded at Finding 50 that Western National was not entitled to contribution and/or reimbursement for benefits paid to the employee under its temporary order, and he ordered Western National alone to pay all benefits at issue other than the permanency that he left undetermined without prejudice.  Western National contends that this conclusion was contrary to the opinion not only of Dr. Hood but also of the treating doctor, Dr. Crowe, and was unsupported by substantial evidence.  It argues that the employee had returned to work unrestricted for over four years after his 1992 surgery before being injured again in 1996 severely enough to require emergency treatment and then again in 1997 severely enough to miss another two weeks of work.  Determination of the permanency of an injury, it argues further, “must include an analysis more complex than a simple consideration of whether there were ongoing symptoms.  If that were the standard, the 1991 injury would be considered a temporary aggravation as well.”  On a policy basis, it argues further that affirmance of the judge’s denial of apportionment between admitted work injuries in a case like this will only have a chilling effect on the willingness of insurers to agree to temporary orders such as Western National agreed to in this case.  We are not persuaded.

Medical experts may differ on substantial contributing causation of a condition, and a compensation judge is entitled to rely on the opinion of an expert other than an employee’s treating physician.  See Caven v. Ag-Chem Equip. Co., Inc., slip op. (W.C.C.A. Sep. 14, 1993), (while a finder of fact may, in appropriate circumstances, choose to afford greater weight to the opinion of a treating physician, the judge is not required to do so); see also Nord, 360 N.W.2d at 342-43, 37 W.C.D. at 372-73.  In this case, it was not unreasonable for the compensation judge to rely on the three expert opinions that supported the judge’s conclusion rather than on the two that did not.  Subsequent to his injury in 1991, the employee underwent a surgical repair procedure that permanently altered his spine, consequent to which alteration he has been compensated for a permanent loss of function.  Expert opinion on which the judge relied has traced the employee’s current condition and need for surgery directly to that 1992 surgery, particularly in light of the employee’s ongoing degenerative disc disease, and we conclude that it was not unreasonable for the judge to rely on that opinion.  With regard to the policy argument, the issuance of a temporary order under Minnesota Statutes section 176.191 is not dependent on the willingness of an insurer, and we foresee no chilling effect as a result of this decision.  The granting of a temporary order does not automatically entitle the paying insurer to contribution or reimbursement.  Because it was not unreasonable, we affirm the compensation judge’s denial of equitable apportionment and of Western National’s petition for contribution and/or reimbursement.  See Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.

The compensation judge’s findings and order in this case run nine single-spaced pages and contain fifty-six findings but only a very brief, one-paragraph memorandum.  Western National contends that the compensation judge was obligated under Minnesota Statutes section 176.371 and Hart v. Evtac Mining Co., slip op. (W.C.C.A. Oct. 31, 2005), to analyze in a more detailed memorandum the three specific work injuries and the one alleged Gillette-type injury that were at issue in this case, to more clearly explain his decisions.  We are not persuaded.

Minnesota Statutes section 176.371 provides in part as follows: