The employers and their insurers appeal from the compensation judge’s findings that (1) the employee’s March 9, 1992, injury was permanent and is a substantial contributing cause of the employee’s current disability; (2) the employee sustained a Gillette injury^[1] culminating on February 1, 2013; (3) the employee suffered a 10% permanent partial disability resulting from the combined effects of the 1992 and the 2013 injuries; (4) the employee was temporarily totally disabled through July 9, 2013; (5) maximum medical improvement was reached on November 27, 2013, for the 2013 injury; and (6) apportioning liability 50/50 between the employers and their insurers.  We affirm as modified.

The employee began working as a truck driver and dock worker for TNT Holland Motor Express, Inc., (TNT) in July 1990.  The employee continued to work for the same employer, but ownership of the company changed several times during the duration of his employment.  In 2013, the company was owned by YRC, Inc./USF Holland (USF Holland).

On March 9, 1992, in the process of loading a semitrailer, the employee leaned over to lift the end of a long box and felt a pop in his lower back followed by immediate pain.  The employee was referred to Multicare Associates where he treated with Dr. Karen Kane.  Dr. Kane diagnosed a lumbar strain/sprain, prescribed non-steroidal anti-inflammatory and muscle relaxant medications, referred the employee to physical therapy, and took the employee off work.

In May 1992, Dr. Kane concluded the employee had reached maximum medical improvement (MMI) with no permanent partial disability and released the employee to return to work without restrictions.  The employee returned to his regular job, but in late June 1992, after doing some heavier work, the employee’s low back pain returned.  Dr. Kane diagnosed a lumbar strain and mechanical low back pain, reimposed restrictions, and referred the employee for additional physical therapy and conditioning.

The employee continued to report good days and bad days, and noted pain radiating from the low back into the buttocks bilaterally.  A CT scan on August 7, 1992, revealed a small, lateral right-sided disc herniation at L4-5.  The employee was referred to Dr. John Dowdle for an orthopedic evaluation.  Dr. Dowdle recommended continued rehabilitation.

The employee continued to report severe back pain, and in October 1992 requested referral for a second opinion.  The employee was seen by Dr. Donald Erickson, a neurosurgeon, on December 2, 1992.  Dr. Erickson concluded that, while the employee was neurologically intact on examination, his MRI and CT scans showed a disc herniation at L4-5 laterally and into the right foramen as well as significant dehydration and degeneration of the L4-5 disc, and recommended a percutaneous discectomy.  The employee underwent the surgery on December 10, 1992.  The operative report describes insertion of a trocar needle into the L4-5 disc.  A cutting suction tip was inserted through the tube and into the nucleus pulposis of the disc.  Fifteen minutes of suction and cutting were performed to remove degenerative disc material.  The employee obtained no relief from the surgery.

On January 6, 1993, a follow-up MRI scan revealed a mild disc bulge and decreased signal in the L3-4 disc and a small right-sided herniated disc at L4-5 contiguous with the nerve root.  A lumbar discogram at L4-5 and L5-S1 on January 14, 1993, showed no evidence of extravasation of the contrast beyond the nucleus pulposis to indicate a tear in the annulus.^[2]  In a January 20, 1993, letter, Dr. Erickson stated the L4-5 and L5-S1 discs appeared anatomically normal on discography and did not produce pain on injection, eliminating the discs as the source of the employee’s pain at that time.  The doctor recommended no further surgery or procedures other than continued conservative care.

Dr. Kane did not believe the employee was ready to return to full duty, and on January 22, 1993, referred the employee to a work hardening program.  The employee completed the program in March 1993.  He reported to Dr. Kane that he was still experiencing some low back and buttock pain.  The doctor diagnosed chronic low back pain and degenerative disc disease, and released the employee to return to work on March 25, 1993, without restrictions.  The employee was last seen by Dr. Kane on June 8, 1993.  He reported persistent low back pain, but stated he was able to tolerate it and was able to do his regular job as a truck driver and dock worker.

The employee testified he still had significant back pain in 1993 and 1994 after returning to work, but that he did eventually improve and the pain was gone by 2003.  The employee received no medical treatment for his back for approximately 20 years, from June 8, 1993, until February 1, 2013.

In 1996, the employee began driving the “Wisconsin route” which he drove until January 28, 2013.  The job consisted of driving a tractor and trailer and delivering and picking up freight from customers.  The employee testified he would leave the terminal with a full load, and that his first stop on average was about an hour away.  He stated he made about 20 stops throughout the day and that the longest period of driving was approximately two hours.  The employee estimated he drove an average of two hundred and fifty to three hundred miles a day and estimated the number of hours worked was between ten to twelve and a half per day.

The employee drove the same tractor every day, but the trailer varied.  The regular semitrailers had roll up doors.  The employee testified he had to get down on one knee, usually on a dock, and open the door pulling up with one hand, and then pull the door back down to the level of the dock to close it, each twenty times a day.  A trailer with a liftgate could be requested for the purpose of unloading at a customer location that did not have a dock.  The liftgate trailer had a portable dock on the back.  The employee testified the dock was heavy, and required physical lifting of two halves weighing approximately sixty or seventy pounds.  He estimated that starting in approximately early to mid-December 2012, he drove a liftgate trailer as much as three times a week.  When he had a liftgate, it was usually used just once during the day for the particular stop it was requested for.

The employee testified that in December 2012, he began to feel a slight pain in his lower back and buttocks that felt like the pain he had experienced in 1992.  He stated he hoped it would resolve on its own, but the pain progressively worsened.  On January 28 or 29, 2013, the employee told USF Holland operations manager, Richard Lechner, that he was experiencing a lot of back pain and needed to go home.  The employee associated his back pain, at that point, with his 1992 injury.

On February 1, 2013, the employee was seen by Dr. Thomas Rieser, an orthopedic surgeon, at the Midwest Spine Institute.  Dr. Rieser diagnosed degenerative disc disease and mechanical low back pain, prescribed pain medication, ordered an MRI scan, and took the employee off work.  The February 5, 2013, scan showed mild disc degeneration at L3-4, a high intensity zone in the posterior right paracentral region at L5-S1, and a broader disc protrusion at L4-5 with endplate osteophyte formation and moderate right and mild to moderate left foraminal narrowing with contact of the exiting L4 nerve roots.  Dr. Rieser concluded there was likely progressive disc deterioration at L4-5 that was causing low back discomfort bilaterally into the buttocks.

In February and March 2013, the employee received three epidural steroid injections bilaterally at L4-5 with mixed results.  The employee also received physical therapy at Westfields Hospital through the end of April 2013 without much improvement.

On March 13, 2013, the employee was seen by Dr. Gary Wyard for an independent medical examination on behalf of USF Holland.  The doctor reviewed the February 5, 2013, MRI scan and concluded it was basically unremarkable.  Dr. Wyard opined the employee had no objective findings on examination to explain his significant back pain and had no objective pathology.  In Dr. Wyard’s opinion, the employee’s back pain was not causally related to his job duties at USF Holland, and his back issues appeared to be longstanding and pre-existing.

The employee returned to see Dr. Rieser on April 30, 2013.  The doctor observed the steroid injections initially seemed to aggravate the employee’s pain, but over time they seemed to help with the pain moving from the low back to the buttocks area.  Dr. Rieser indicated the employee’s pain was better than it was three months previously, felt the employee had plateaued in recovery, and believed the employee could attempt a return to work if he used good techniques for lifting and bending.  Dr. Rieser completed a workability form providing for a return to work on May 6, 2013, eight hours per day.

USF Holland operations manager Lechner testified it was the employer’s policy that an employee could not return to work with restrictions.  The employer referred the employee to Dr. Orrin Mann at Multicare Associates for a return to work evaluation.  On May 9, 2013, Dr. Mann concluded the employee needed to demonstrate in a controlled setting the ability to work within the requirements of the job, and in a May 10, 2013, letter, advised the employer he could not clear the employee to return to unrestricted duty at that point.  On May 14, 2013, Dr. Rieser referred the employee to OSI Physical Therapy for work conditioning.

On May 24, 2013, the employee sought a second opinion regarding treatment options at the Mayo Clinic.  Gary Kadlec, a certified nurse practitioner (CNP), assessed multilevel degenerative changes in the lumbar spine with axial low back pain, and concluded the focus of care should be nonoperative.  CNP Kadlec suggested facet injections to see if they would be more beneficial.  Bilateral L4-5 and L5-S1 facet joint injections were performed at the Mayo Clinic on June 10, 2013.  The employee initially reported his pain worsened following the injections, and on June 20, 2013, CNP Kadlec recommended a pain clinic consultation.  On June 24, 2013, however, the employee contacted the Mayo Clinic and reported that he felt better than he had felt in six months and cancelled the pain clinic appointment.

On June 25, 2013, OSI reported the employee had made steady improvement in functional strengthening and met the demands of the job description provided by USF Holland.  The employee was discharged from therapy.  That same day, the employee met with Dr. Rieser who noted the employee’s second opinion at Mayo Clinic.  The doctor concluded, based on the OSI functional capacity assessment, that the employee could return to full duty work without restrictions on July 1, 2013.

Dr. Rieser further concluded it was reasonable to proceed with diagnostic medial branch facet nerve blocks from L2 through L5 which were performed on July 2, 2013.  In the recovery room, the employee had about a 50% reduction of pain, indicating that the facet joints, although perhaps contributing to the employee’s symptoms, were not the exclusive pain generators.

The employee was seen in follow-up by Dr. Mann on July 9, 2013, who stated he agreed with the employee’s physical therapist and Dr. Rieser, and released the employee to resume unrestricted duty.  The employee returned to work with employer USF Holland on July 10, 2013, in a full duty dock only position.

The employee continued to receive medical care after returning to work.  In July and September 2013, Dr. Louis Saeger assessed bilateral posterior hip and upper buttock pain of suspected sacroiliac (SI) joint origin and provided epidural injections into the left and right SI joints with some relief.  The employee also returned to OSI Physical Therapy on October 11, 2013, seeking further relief of chronic low back pain.  The employee received treatment at OSI through November 27, 2013.

On March 12, 2014, Dr. Thomas Raih performed an independent medical examination on behalf of TNT.  By report dated March 24, 2014, Dr. Raih concluded the employee had generalized back pain compatible with multilevel degenerative disc disease and a history of a prior injury at L4-5 in 1992 from which the employee had a complete functional recovery.  The doctor opined the employee sustained a Gillette-type injury, culminating in December 2012, that was a permanent aggravation of underlying degenerative disc disease.  Dr. Raih opined the employee’s medical treatment to date had been reasonable and necessary and that the employee had reached maximum medical improvement.  The doctor assigned a 10% permanent partial disability which he attributed to the employee’s 2013 degenerative disc condition and not the March 9, 1992, injury.  In Dr. Raih’s opinion 100% of the employee’s medical treatment and work restrictions since December 2012 were related to the Gillette injury.

In a December 18, 2014, narrative report, Dr. Rieser opined that the current cause of the employee’s low back pain was a permanent aggravation of underlying degenerative disc and facet disease at L3-4, L4-5, and L5-1, and that the L4-5 level was somewhat more advanced than the other levels.  In the doctor’s opinion, although the employee was over 20 years post the 1992 discectomy, the surgery predisposed the employee to degeneration at the L4-5 level.  Dr. Rieser felt the bigger player was the employee’s work activities over the past 20 years as a truck driver with prolonged sitting, repetitive bending, and lifting in the process of delivering freight, and apportioned 80% of the employee’s current condition to a Gillette injury culminating on February 1, 2013, and 20% to the 1992 injury.

The employee filed a Claim Petition on April 26, 2013, alleging a Gillette injury on February 1, 2013, while employed by USF Holland.  The employee sought temporary total and permanent partial disability benefits and payment of medical expenses.  USF Holland denied primary liability.  The employee filed an Amended Claim Petition on February 5, 2014, adding the March 9, 1992, injury while employed by TNT.  TNT admitted the employee sustained an injury on that date, but denied liability for the employee’s current disability and need for medical treatment.  In a Findings and Order served and filed June 4, 2015, the compensation judge found (1) the employee’s March 9, 1992, low back injury was permanent and was a substantial contributing cause of his current condition; (2) the employee sustained a Gillette injury culminating on February 1, 2013, that was a permanent aggravation of the employee’s pre-existing condition resulting from the March 9, 1992, injury; (3) the employee was temporarily and totally disabled from February 1 to July 9, 2013, as a substantial result of both injuries; (4) the employee reached maximum medical improvement from the February 1, 2013, injury as of November 27, 2013; (5)  the employee was entitled to a 10% permanent partial disability as a substantial result of both injuries; (6) the medical treatment paid for by the intervenor Health and Welfare Fund was reasonable and necessary as a substantial result of both injuries; and (7) apportioned the employee’s need for medical treatment and restrictions 50/50 between the two injuries.  Both employers and their insurers appeal.

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 persuasive Dr. Rieser’s opinion that the March 9, 1992, injury was permanent and predisposed the employee to lumbar spine degeneration.  In her memorandum, the compensation judge explained that while the employee’s credible testimony and medical records established that his symptoms following the 1992 injury eventually resolved and he did not have periodic or intermittent flare-ups of low back and buttock pain over the years, the evidence supported the conclusion that the March 9, 1992, injury was permanent.  The judge concluded the injury and resulting surgery damaged the L4-5 disc, predisposing the employee to further degeneration at L4-5, and making him susceptible to reinjury.

Appellants TNT/CNA argue the compensation judge’s finding is not supported by substantial evidence and is clearly erroneous.  They assert the January 7, 1993, MRI scan showed normal height lumbar discs, and that Dr. Erickson, after reviewing the January 14, 1993, discogram, indicated that both the L4-5 and L5-S1 discs were “anatomically normal” and did not produce pain on injection.  The appellants contend the L4-5 disc herniation was clinically insignificant, and argue the fact that there was a small disc herniation at L4-5 before and after the 1992 surgery “that was not causing the employee’s symptoms” does not support the conclusion that the March 1992 injury was permanent.

The appellants additionally contend that Dr. Rieser’s opinion is without adequate foundation.  TNT/CNA assert that while Dr. Rieser stated the L4-5 degeneration in 2013 was more advanced than the other levels, he ignored that the disc height was normal in 1993, and further ignored the fact that the employee had degenerative changes at other levels in 2013 that no medical provider ever opined were the source of the employee’s low back symptoms in 1993.

It is undisputed the employee sustained a work-related injury to his low back on March 9, 1992.  CT and MRI scans following the 1992 injury revealed a disc herniation at L4-5 laterally and into the right foramen, as well as significant dehydration and degeneration of the L4-5 disc.  Nor is there any question that in December 1992 Dr. Erickson performed a percutaneous discectomy at L4-5, consisting of suction and cutting to remove degenerative disc material, as a result of the 1992 work injury.  The January 6, 1993, follow-up MRI scan showed a mild disc bulge and decreased signal in the L3-4 disc and a small right-sided lateral herniated disc at L4-5 contiguous with the nerve root.  The January 14, 1993, discogram showed only the absence of a tear in the annulus fibroses around the L4-5 or L5-S1 discs, thus Dr. Erickson concluded he had no further surgical procedures to offer.

Upon examination of the employee on February 1, 2013, Dr. Rieser suspected disc degeneration at L4-5.  The February 5, 2013, MRI scan revealed a bulging disc at L4-5 with endplate osteophyte formation and moderate right side and mild to moderate left side foraminal narrowing with encroachment on the L4 nerve root.  It was Dr. Rieser’s opinion that the employee had progressive deterioration of the L4-5 disc as well as degeneration at L3-4 and L5-S1.  The doctor explained that although the employee was 20 years post discectomy, the 1992 surgery predisposed the employee to degeneration of the L4-5 level.  It is clear the 1992 discectomy was clinically significant to Dr. Rieser, and his opinion that the surgery made the L4-5 disc more susceptible to degeneration has adequate foundation.  Since Dr. Rieser’s opinion has adequate foundation, the compensation judge’s choice of medical expert opinion must be upheld.  See Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985).  Substantial evidence supports the compensation judge’s finding that the employee sustained a permanent injury on March 9, 1992, and we affirm.

The compensation judge adopted Dr. Rieser’s opinion and found the employee sustained a Gillette injury to his low back arising out of his employment with USF Holland culminating on February 1, 2013, that was a permanent aggravation of the employee’s pre-existing condition resulting from the March 9, 1992, injury.  The judge noted that Dr. Raih also opined the employee sustained a Gillette-type, permanent aggravation of his underlying degenerative disc disease culminating in December 2012.  Cross-appellant USF Holland argues the compensation judge’s finding of a Gillette injury on February 1, 2013, is not supported by the evidence as a whole, and that Dr. Rieser’s opinion lacks foundation and was erroneously relied upon by the compensation judge.

The question of a Gillette injury primarily depends on medical evidence.  Steffen v. Target Stores, 517 N.W.2d 579, 581, 50 W.C.D. 464, 467 (Minn. 1994).  The employee’s burden of proof requires the medical expert have some appreciation of the nature of the employee’s work duties that can be causally linked with the employee’s disability.  To have adequate foundation, the facts upon which an expert relies for his or her opinion must be supported by the evidence.  See, e.g., Grieger v. Viking Collections, 62 W.C.D. 54 (W.C.C.A. 2001).

The cross-appellant argues that both Dr. Rieser and Dr. Raih assumed facts not in evidence and described those facts as significant in arriving at their opinions.  In particular, USF Holland asserts that Dr. Rieser was asked to assume certain facts set forth in the employee’s attorney’s letter to him that are incorrect.  The cross-appellant further states that the employee in his brief misstates the record and, in relying on these misstatements, further argues that the employee’s job duties were discussed with Dr. Rieser and memorialized in the doctor’s chart notes which USF Holland asserts is not true.

The compensation judge concluded the employee testified credibly that he explained his job duties to Dr. Rieser, including lifting the trailer doors, opening and closing the liftgate, prolonged sitting, and carrying freight.  In his chart note on February 6, 2013, Dr. Rieser noted “truck driver, does loading and unloading;” on February 22, 2013, the doctor noted the employee “has been doing truck driving, lifting, bending, and prolonged sitting;” and on March 29, 2013, he noted the employee “has been a truck driver for a number of years and recently his job has involved repetitive lifting, bending and twisting, lifting up a very heavy tailgate door.”  (Pet. Ex. F.)  A YRC, Inc./USF Holland Essential Physical Requirements statement provided to Dr. Mann and Dr. Rieser in May 2013 indicates the employee’s job required the ability to sit for extensive periods of time; frequently lift up to 55 pounds, occasionally lift up to 70 pounds and seldom lift up to 100 pounds; and the ability to perform repetitive tasks including stretching, turning, twisting, bending, crouching, squatting, kneeling and stooping for extensive periods of time.  In his December 18, 2014, narrative report, Dr. Rieser ascribed the Gillette injury to the “prolonged work [the employee] has been doing over the past 20 years as a truck driver with prolonged sitting, repetitive bending, lifting, in the process of delivering freight.”  (Pet. Ex. A.)

Based on the employee’s testimony and the medical records submitted at the hearing, the judge found the employee’s ordinary work duties on the Wisconsin route put repetitive stress on his low back, and that using the liftgate put additional strain on the employee’s low back.  In her memorandum the compensation judge observed the employee testified in some detail about his job duties and concluded that Dr. Rieser’s notes demonstrated a fairly accurate and complete understanding of the stresses that the employee’s job duties on the Wisconsin route put on his back.

Assessment of a witness’s credibility is the unique function of the trier of fact.  Even v. Kraft, Inc., 445 N.W.2d 831, 834-35, 42 W.C.D. 220, 225 (Minn. 1989).  This court must give due weight to the opportunity of the compensation judge to judge credibility.  It is not the role of the WCCA to make its own evaluation of the credibility and probative value of witness testimony or to choose inferences from the evidence different from those of the compensation judge.  Redgate v. Sroga's Standard Serv., 421 N.W.2d 729, 734, 40 W.C.D. 948, 957 (Minn. 1988).  Moreover, it is the province of the compensation judge, as the trier of fact, to resolve conflicts in expert medical testimony.  This court generally upholds a compensation judge’s choice among expert medical opinions unless the expert opinion assumes facts that are not supported by the evidence.  See Nord v. City of Cook, 360 N.W.2d 337, 342-43, 37 W.C.D. 364, 372-73 (Minn. 1985).  Multiple competing medical opinions regarding the existence of a Gillette injury were submitted at the hearing.  The compensation judge did not abuse her discretion in adopting the opinion of Dr. Rieser, and substantial evidence supports the compensation judge’s determination that the employee sustained a Gillette injury to his low back arising out of his employment with USF Holland culminating on February 1, 2013.

The cross-appellant additionally argues that the compensation judge ignored the employee’s history of depression, anxiety, and psychological treatment seeking behaviors in both 1992-93 and 2013.  Dr. Rieser, USF Holland asserts, at no time addressed the employee’s psychological complaints and demonstrated no recognition of the employee’s reports of depression and anxiety.

The compensation judge in her memorandum acknowledged USF Holland’s argument that the employee’s low back complaints were not the result of a work injury but were either the result of psychological issues or related to sleep apnea.  The judge concluded, however, that the evidence showed the employee has objective abnormalities at L3-4 and L4-5 that correspond with his complaints of pain, and that, based on his credible testimony, the employee seemed unusually motivated to continue working despite the problems he had with his back.  And finally, the judge explained, the employee kept working for approximately a year after he discussed mild depression and trouble sleeping with his primary care physician and based on the employer’s witnesses’ testimony, his work was exemplary.  The compensation judge’s conclusions are consistent with the record.  Moreover, there was no evidence that the employee’s anxiety or depression affected his ability to work, and no medical expert opinion that the employee’s disability was caused or contributed to by any psychological issues.  We, accordingly, affirm.

The compensation judge apportioned the employee’s need for medical treatment and restrictions 50% to the March 9, 1992, injury and 50% to the February 1, 2013, injury.  The judge acknowledged that Dr. Rieser and Dr. Raih attributed the major portion of responsibility to the February 1, 2013, injury, but found it equitable to assign more responsibility to the initial injury than suggested.  The compensation judge concluded the March 9, 1992, injury set in motion the process that predisposed the employee to degeneration in the lumbar spine, particularly at L4-5, and that the associated degeneration has been the employee’s primary pain generator since February 1, 2013.  The employee’s work duties on the Wisconsin route rendered the pre-existing condition symptomatic again, and the judge concluded that each was a necessary and equally contributing factor to the employee’s 2013 disability.

Appellants TNT/CNA assert that the evidence does not support a 50/50 apportionment between a 20-year-old injury that resolved many years ago and a 2013 Gillette multilevel disc injury.^[3]  They reiterate their argument that the employee’s 1992 injury involved non-discogenic pain, that the injury resolved without permanency, and that Dr. Rieser’s statement that the 1992 percutaneous discectomy predisposed the employee to difficulties is without evidentiary support.  TNT/CNA further point out that no medical expert assigned a 50/50 apportionment.

Cross-appellant USF Holland similarly asserts, again, that the “undisputed” findings in 2013 were normal lumbar examinations, severe lumbar pain complaints not substantiated by objective findings, pain complaints not aggravated by activity, and the employee’s depression and anxiety, and argues that substantial evidence does not support the compensation judge’s apportionment findings.

Equitable apportionment is available to prescribe contribution between two or more employers or insurers that may be liable for an employee’s disability.  Equitable apportionment is not merely a medical determination, and can, of necessity, be based on no predetermined and precise formulas, but must be determined on the facts of each case.  Goetz v. Bulk Commodity Carriers, 303 Minn. 197, 226 N.W.2d 888, 27 W.C.D. 797 (1975).

Here, the medical evidence is extensive and the medical opinions on apportionment widely varied.  In Dr. Wyard’s opinion, the employee’s back pain was not causally related to his job duties at USF Holland and 100% of the employee’s disability was attributable to his longstanding, pre-existing degenerative condition.  Dr. Raih attributed 100% of the employee’s disability to the 2013 Gillette injury, and Dr. Rieser allocated 80% to the 2013 Gillette injury and 20% to the March 9, 1992, injury.  Where the record would support any number of apportionment determinations, this court will not substitute our judgement for that of the compensation judge.  Giem v. Robert Giem Trucking, 46 W.C.D. 409 (W.C.C.A. 1992); compare Sundquist v. Kaiser Eng’rs, Inc., 456 N.W.2d 86, 42 W.C.D. 1101 (Minn. 1990).

Appellants TNT/CNA also argue that the compensation judge by asserting the February 1, 2013, Gillette injury was caused in part by the March 9, 1992, injury is essentially attempting to apportion a single Gillette injury.  A Gillette injury, they argue, may not be apportioned in the absence of uncontroverted medical evidence.  The appellants contend there is no uncontroverted evidence of a permanent 1992 injury and apportionment is therefore not appropriate.  The supreme court has upheld a compensation judge’s equitable apportionment of liability between a specific injury followed some years later by a Gillette injury.  See Sundquist, id.  The compensation judge found the March 9, 1992, injury was permanent and was a contributing cause of the employee’s subsequent disability, and properly determined equitable apportionment between the two injuries.  We affirm.

The compensation judge relied on the opinion of Dr. Raih and awarded a 10% permanent partial disability pursuant to Minn. R. 5223.0390, subp. 3.C.(2), based on persistent lumbar pain, abnormal findings on the February 5, 2013, MRI scan, and persistent limited range of motion and decreased function documented in the employee’s medical records.  Dr. Raih attributed the permanency solely to the February 1, 2013, Gillette injury.  The compensation judge, however, found the employee was entitled to the 10% permanent partial disability as a substantial result of both injuries, and ordered the “employers and insurers” to pay.

The cross-appellant argues the finding of a 10% permanency resulting from the combined effects of the 1992 and the 2013 injury is clearly erroneous as a matter of law and unsupported by substantial evidence.  USF Holland argues that the employee’s clinical presentation is notable for the absence of persistent objective clinical findings such as involuntary muscle tightness or decreased range of motion in the lumbar spine.  Any such findings, the cross-appellant contends, are not persistent, but only occasional.

There is some merit to USF Holland’s argument.  However, Dr. Raih reviewed the medical records, including all records introduced into evidence at the hearing, and performed an examination of the employee on March 12, 2014.  In making his rating, the doctor relied on findings of decreased range of motion on his examination and similar findings noted in the chart notes of Dr. Rieser, the physical therapy records, and the Mayo Clinic records.  There is adequate evidence to support Dr. Raih’s rating.

USF Holland further argues that Minn. R. 5223.0250 requires that a permanency rating for a disabling condition must be reduced by the rating assigned to a pre-existing disability.  The cross-appellant asserts the compensation judge failed to consider 9% permanency paid to the employee as a result of the 1992 injury.  Applying the calculations required by the rule, the amount due after apportionment for the pre-existing condition would be 3.6%.  USF Holland argues the award of permanency should be modified accordingly.

There was, however, no evidence at the hearing that the employee received a 9% permanent partial disability rating for the 1992 injury.  The only evidence was that Dr. Kane, in May 1992, provided a 0% permanent partial disability rating.  Appellant TNT/CNA asserts the 0% permanency rating was never challenged and was not one of the issues before the compensation judge.

The compensation judge did not, in her findings, specifically apportion liability for the employee’s 10% permanent partial disability.  In her memorandum, the compensation judge concluded that the two injuries contributed equally to the “employee’s condition” after February 1, 2013.  Ordinarily, permanent partial disability benefits are to be apportioned pursuant to Minn. Stat. § 176.101, subd. 4a.  However, it appears that statutory apportionment was not raised below and was not at issue in this case.  Moreover, even if statutory apportionment were applicable, the reduced apportionment sought by USF Holland is not possible since no medical report or record was submitted establishing loss of use or impairment of function prior to February 1, 2013.  See Britton v. NCHP Property Mgmt., 43 W.C.D. 406 (W.C.C.A. 1990); Frampton v. Cub Foods, No. WC04-194 (W.C.C.A. Jan. 10, 2005).

In Stone v. Lakehead Constructors, 533 N.W.2d 36, 52 W.C.D. 637 (Minn. 1995) and Gordon v. Ryder Student Transp., 52 W.C.D. 661 (W.C.C.A. 1994), summarily aff’d 537 N.W.2d 287(Minn. 1995), the supreme court applied the principles of equitable apportionment to allocate responsibility for the employee’s permanent partial disability benefits.  Where the facts and circumstances do not lend themselves to the arithmetic method set forth in the statute and rules, a compensation judge has discretion to resolve the apportionment issue by application of equitable apportionment.  See e.g, Zidich v. Nat’l Cash Register Corp., 54 W.C.D. 348 (W.C.C.A. 1996).  We, accordingly, modify the compensation judge’s order to apportion responsibility for the employee’s 10% permanent partial disability 50% to TNT and 50% to USF Holland, consistent with the judge’s apportionment of liability for medical treatment and restrictions.

The compensation judge found the employee was temporarily and totally disabled from February 1 through July 9, 2013.  Cross-appellant USF Holland argues the employee’s disability ended on April 30, 2013, at the latest.  USF Holland asserts the employee was released to return to work by Dr. Rieser on that date, and that both Dr. Wyard’s examination on March 20 and Dr. Rieser’s on April 30 produced normal physical findings.  Citing Kautz v. Setterlin Co., 410 N.W.2d 843, 40 W.C.D. 206 (Minn. 1987), the cross-appellant argues that when an employee is medically able to return to his former work without restrictions, he is not entitled to wage loss benefits.

In this case, however, Dr. Rieser imposed an eight hour work restriction that the employer was not willing to accommodate, and notes from the employee’s physical therapist indicated the employee might not have the physical capabilities required for the truck driving and dock worker position.  In addition, the employee was eventually rated with a 10% permanent partial disability.

The employer referred the employee to Dr. Mann, who on May 10, 2013, advised the employer he could not clear the employee to return to unrestricted duty at that point.  On May 14, 2013, Dr. Rieser referred the employee to OSI Physical Therapy for work conditioning and hardening.  Following completion of the OSI program, including certification that the employee met the demands of the job description provided by YRC, Inc./USF Holland, and review by Dr. Rieser and Dr. Mann, the employee was released to return to work by Dr. Mann on July 9, 2013, without restrictions.  The employee returned to work with USF Holland on July 10, 2013, in a full duty dock only position.

The cross-appellant, however, argues the employee failed to make a diligent search for work prior to returning to his work with the employer on July 10, 2013.  When released to return to work by Dr. Rieser, effective May 6, 2013, the employee testified he intended to return to work with USF Holland but was unable to do so by the employer’s inability to accommodate his restrictions and the employer’s requirement that he see Dr. Mann and undergo the recommended physical therapy.  An employee may be excused from the obligation to make a job search if there is a reasonable expectation that the employee will be returning to work with the date-of-injury employer.  Redgate v. Sroga's Standard Serv., 421 N.W.2d 729, 734 n.4, 40 W.C.D. 948, 956 n.4 (Minn. 1988); Glasow v. Gresser Concrete, slip op. (W.C.C.A. Apr. 18, 1995).  The employee had been employed by the employer since 1990 and both the employer and the employee anticipated that he would return to work with USF Holland upon completion of work hardening and a work release with no restrictions.

Substantial evidence supports the compensation judge’s determination that the employee was entitled to temporary total disability benefits through July 9, 2013, and we affirm.

The compensation judge found the employee reached maximum medical improvement (MMI) from the February 1, 2013, injury as of November 27, 2013, the date he last attended physical therapy at OSI.  USF Holland argues the employee reached MMI no later than April 30, 2013.  The cross-appellant contends that no medical record thereafter or any testimony demonstrated any significant improvement beyond the employee’s normal findings on examination and subjective pain complaints.

MMI means the date after which no further significant recovery from or significant lasting improvement from an injury can reasonably be anticipated, regardless of subjective complaints of pain.  Minn. Stat. § 176.011, subd. 25.  A finding of MMI is one of ultimate fact.  It is the responsibility of the compensation judge to evaluate the employee's condition as documented by medical records, medical opinions, and other data and circumstances.  Hammer v. Mark Hagen Plumbing & Heating Co., 435 N.W.2d 525, 41 W.C.D. 634 (Minn. 1989).

The medical records reflect improvement in the employee’s condition as a result of the treatment he received from Dr. Rieser, Dr. Saeger, Dr. Mann, OSI Physical Therapy, and the Mayo Clinic through September 19, 2013.  On April 30, 2013, Dr. Rieser provided a work release limiting the employee to 8 hours a day.  Dr. Mann was unwilling to clear the employee to return to unrestricted duty, and Dr. Rieser referred the employee to OSI Physical Therapy.  The employee participated in a work conditioning program at OSI from May 16 through June 25, 2013.  The therapy notes reflect gradual improvement in the employee’s low back and buttock symptoms and significant functional improvement.

The employee also sought a second opinion regarding additional treatment options at the Mayo Clinic on May 24, 2013.  On June 10, 2013, the employee received bilateral L4-5 and L5-S1 facet joint injections at the clinic.  The employee contacted the clinic on June 24, 2013, reporting that he felt better than he had in six months.

On July 2, 2013, the employee received medial branch facet nerve blocks at L2 through L5 performed by Dr. Saeger.  In the recovery room the employee reported about a 50% reduction in pain.  In July and September 2013, Dr. Saeger assessed bilateral posterior hip and upper buttock pain of suspected sacroiliac (SI) joint origin and performed epidural injections into the left and right SI joints providing significant pain relief.

From October 11, 2013, through October 31, 2013, the employee participated in a low back stabilization program at OSI Physical Therapy.  The treatment records evidence some decrease in low back pain and improvement of motion through October 31, 2013.  However, on November 7, 2013, the employee reported worsening pain over the past week and there is no evidence of any improvement in the employee’s condition in the therapy records after that date.  We, therefore, modify the judge’s determination, concluding the employee reached MMI on October 31, 2013, from the February 1, 2013, injury.

The compensation judge found that the medical treatment paid for by the intervenor, Central States SE and SW Area Health and Welfare Fund, was reasonable and necessary as a substantial result of both the 1992 injury and the 2013 injury.  The cross-appellant argues the finding is not supported by substantial evidence.  USF Holland asserts that medical treatment after April 30, 2013, was based exclusively on the employee’s self-referral and there was no statement of medical necessity provided by any physician.  The cross-appellant again argues that the medical treatment after April 30, 2013, did not change the employee’s physical abilities, reduce his subjective complaints, or result in a change in clinical examination.

The cross-appellant’s argument is essentially a restatement of the arguments it presented regarding MMI.  Although the employee sought a second opinion from Mayo Clinic on his own, Dr. Rieser was clearly aware of and noted the care received by the employee at the clinic.  The fact that there was no referral to OSI in October 2013 by a physician is not in itself evidence that the treatment was not reasonable and necessary.  It is, rather one factor for the compensation judge to weigh in determining the reasonableness and necessity of the treatment.  In addition, Dr. Raih conducted an examination of the employee on March 24, 2014, and reviewed the employee’s treatment records.  In Dr. Raih’s opinion, the employee’s treatment to date was reasonable and necessary.  There is substantial evidence to support the compensation judge’s finding that the medical treatment paid for by the intervenor on behalf of the employee was reasonable and necessary as a result of both injuries, and we affirm.