JEFFREY WARD, Employee/Appellant, v. CITY OF ST. LOUIS PARK, SELF-INSURED/SEDGWICK CLAIMS MGMT. SERVS., Employer, and ANESTHESIOLOGY P.A., NORTH MEM=L HOSP., and MEDICA HEALTH PLAN, Intervenors.

 

WORKERS= COMPENSATION COURT OF APPEALS

DECEMBER 7, 2005

 

No. WC05-183

 

HEADNOTES

 

EVIDENCE - EXPERT MEDICAL OPINION.  Where the employer=s independent medical examiner did not improperly rely on the operative reports of the employee=s treating surgeon and the MRI reports of the attending radiologists rather than on arthroscopic photographs and the MRI films themselves, and where the IME=s unawareness of the treating surgeon=s diagnosis of chondromalacia at the time of an earlier surgery was essentially moot under the facts of the case, the court would not conclude that the IME=s otherwise well developed opinions were without adequate foundation to be relied upon by the compensation judge.

 

CAUSATION - SUBSTANTIAL EVIDENCE; CAUSATION - INTERVENING CAUSE; EVIDENCE - BURDEN OF PROOF.  A compensation judge is free to accept a portion of an expert's opinion while rejecting other portions.  Where the employee did not complain of left knee pain to a doctor for ten years after his 1994 work injury, and where neither of the parties in their opening statements nor the judge in her decision ever invoked the legal theory of a Asuperseding intervening cause,@ the judge=s conclusion that the employee=s surgery after a knee injury at home in 2004 was unrelated to the 1994 work injury was not clearly erroneous and unsupported by substantial evidence, notwithstanding the fact that the judge, without shifting the burden of proof to the employer, relied on the opinion of an independent medical examiner who voluntarily referred to the 2004 injury as a Asuperseding intervening injury.@

 

Affirmed.         

 

Determined by: Pederson, J., Johnson, C.J., and Stofferahn, J.

Compensation Judge: Peggy A. Brenden

 

Attorneys: Gary L. Manka, Katz, Manka, Teplinsky, Due & Sobol, Minneapolis, MN, for the Appellant. Jay T. Hartman, Heacox, Hartman, Koshmrl, Cosgriff & Johnson, St. Paul, MN, for the Respondent.

 

 

OPINION

 

WILLIAM R. PEDERSON, Judge

 

The employee appeals from the compensation judge's conclusion that certain work injuries beginning in 1994 were not substantial contributing factors in the employee=s need for left knee arthroscopic surgery in September of 2004.  We affirm.

 

BACKGROUND

 

Jeffrey Ward began working as a firefighter for the St. Louis Park Fire Department in 1981.  Mr. Ward=s employment with the St. Louis Park Fire Department [the employer] has been marked by numerous work-related injuries to both of his knees and to his low back, beginning in 1994.  On July 14, 1994, Mr. Ward [the employee] sustained an injury to his right knee when he stepped off a curb and twisted that knee in the course of his employment.  Later that same year, on October 13, 1994, the employee injured also his left knee, in the process of attempting to open a garage door.  The employee was thirty-eight years old on the date of this injury and was earning a weekly wage of $924.70.  An MRI scan on November 4, 1994, revealed a tear of the mid aspect of the inferior surface of the posterior horn of the medial meniscus, with no evidence of a lateral meniscus tear or of cruciate or collateral ligament instability.  On November 21, 1994, Dr. Kraft performed an arthroscopic partial medial meniscectomy on the employee=s left knee, repairing a Aflap tear@Ain the mid-portion going posteriorly@ of the meniscus by removing one-half gram of cartilage - - less than fifty percent of the meniscus, leaving the remaining meniscus Aquite stable.@  In the process of the surgery, Anormal articular cartilage in the femoral condyle and the tibial plateau were noted.@  On December 14, 1994, the employee returned to work on a restricted basis.  In treatment notes for February 1, 1995, Dr. Kraft noted that the employee had full range of motion in the knee and no tenderness medially, although there was Aa little bit of tenderness along the patellar and a little crepitance indicating that there is some mild chondromalacia patella.@  Dr. Kraft went on to inform the employee on that date, however, that Athe meniscal injury is healed well at this point,@ and he released the employee to return to Afull and unrestricted work.@

 

Beginning in the late 1990s, Department firefighters began responding to medical as well as fire calls, and the total number of calls handled by the Department annually increased dramatically from about six or seven hundred to nearly three thousand.  Over the course of the nine-year period from his release to work on February 1, 1995, through July 12, 2004, the employee evidently experienced intermittently recurring left knee symptoms, including occasional soreness and some  Apopping@ or Acatching@ that would spontaneously resolve in a matter of seconds.  During that same period, he evidently would sometimes self-treat these left-knee symptoms with ice and/or Tylenol or would wear a sleeve on the knee as a precaution, but he never saw a doctor regarding that knee and was subject to no restrictions related to it.  He did, however, report to the employer - - and the employer has acknowledged liability for - - ten additional instances of work-related injury to that knee as well as to his right knee and his low back, receiving medical attention only for the right knee and low back injuries.

 

The ten reported work injuries between February 1, 1995, and July 12, 2004, were as follows.  On February 22, 1995, the employee sustained an injury to both of his knees when he became entangled in a fire hose while fighting a fire.  On March 9, 1995, he sustained partial tears of the posterior meniscus and anterior cruciate ligament in his right knee when he slipped on some ice in a nursing home parking lot, the latter tear subsequently being repaired by Dr. Kraft arthroscopically.  On August 21, 1995, he evidently injured the right knee again in a house fire and then experienced increased soreness in that same knee two days later while bending down in the fire station kitchen.  This injury was diagnosed in the emergency room as a Aprobable meniscus injury,@ and the employee was referred for an orthopedic consultation.  The following year, on April 14, 1996, while lifting a gurney, the employee experienced renewed right knee soreness, which was subsequently diagnosed as a first degree sprain.  The employee was released to return to his job on April 23, 1996, and about five months later, on September 7, 1996, he experienced increased soreness in that same right knee as he was stepping out of a fire engine.  Dr. Kraft explored and repaired the knee arthroscopically on November 13, 1996, and the employee was released to return to his job without restrictions on December 9, 1996.  About a year and a half later, on May 20, 1998, the employee experienced increased right-knee soreness in the process of restraining an emergency patient in the throes of an epileptic seizure.  By June 19, 1998, he was Afeeling pretty normal once again,@ and Dr. Kraft released him to full and unrestricted work activities, anticipating no associated long term disability.  On August 24, 2000, the employee experienced returned right-knee soreness, in the process of lifting a large woman.  On March 1, 2001, he sustained yet another injury to his right knee, in the process of lifting a patient who had fallen.  Dr. Phillip Johnson=s treatment notes on March 4, 2001, report that the employee had in the past had surgery also on the left knee but that A[t]hat is not giving him any problems.@  The employee was taken off work for a week and then released again on March 19, 2001, to return to his regular job.  On March 28, 2001, the employee underwent an MRI scan of the right knee, which was read to reveal some degenerative changes in the posterior horn and body of the medial meniscus but without any discrete tear.  On October 18, 2001, Dr. Kraft issued a health care provider report, on which he indicated that the employee had reached maximum medical improvement with regard to his March 1, 2001, right knee injury, having sustained no permanent partial disability.  About a year later, on March 24, 2002, he experienced a popping accompanied by pain in his left knee at work while checking a tire, but he did not seek any medical attention for the symptoms.  On September 16, 2002, the employee sustained a work-related injury to his low back while lifting a fan out of a fire truck.

 

After undergoing physical therapy for his back and being alternately released and restricted from working due to his continuing back pain, the employee underwent thoracic and lumbar MRI scans on November 6, 2002, which were read to reveal mild to moderate both disc protrusion and spinal stenosis from T8 through T12 and from L4 through S1 - - without, however, any nerve root compression.  On January 15, 2003, the employee was examined by neurosurgeon Dr. Gregory Harrison, who, referencing complaints by the employee of pain only in his right knee and low back, recommended continuing conservative care, including deliberate avoidance of heavy lifting.  The employee was ultimately forced by his low back pain to retire from his job as a firefighter, and he was thereafter treated for related depression for much of 2003, while his low back pain apparently increased.  On April 22, 2003, the employee was examined for the employer by orthopedic surgeon Dr. Mark Engasser, who diagnosed a work-related disc herniation at L5-S1 from which he had not yet reached maximum medical improvement [MMI].  Finding no compression documented on a CT scan/myelogram, Dr. Engasser recommended a functional capacities evaluation [FCE] to establish some permanent work restrictions.  On August 4, 5, and 6, 2003, the employee underwent an FCE related primarily to his September 2002 back injury, the report of which FCE indicated in part that his A[k]nees do not present any functional problems.@  An anatomical diagram on that report indicated that the employee was experiencing slight numbness in the right leg and pain in the right low back, but no symptoms were noted on the left leg on the diagram.  On August 25, 2003, Dr. Engasser recommended against low back surgery but rated the employee=s low-back-related permanent impairment at 12% of the whole body.

 

On July 12, 2004, about a year after his FCE, the employee saw Dr. Paul Lysne for left knee pain, complaining that on July 11, 2004, the knee had locked up on him and that he was now having difficulty fully extending it.  Dr. Lysne noted on that date that A[t]en years ago, [the employee] had a Left Meniscectomy@ and A[h]as had some pain intermittently in the knee since this time.@  X-rays of the knee showed no degenerative changes, and Dr. Lysne ordered an MRI scan.  The scan was conducted on July 16, 2004, and was read to reveal what radiologist Dr. Peter Constantini identified as findings Acompatible with an oblique tear@ but ones that Acould well represent an old tear which has been surgically repaired.@  The employee was eventually referred back to Dr. Kraft again, who saw the employee on August 5, 2004, and reported that the employee Arelates that [his left knee] cracked as he was twisting and going down a stair and he had immediate pain.@  After reviewing the employee=s MRI scan, Dr. Kraft concluded that the employee Adoes have what appears to be a torn medial meniscus in the posterior aspect of the meniscus body.@  On that diagnosis, Dr. Kraft recommended arthroscopic surgery and released the employee to continue working, restricted from doing any squatting, crouching, kneeling, or lifting over ten pounds.  On August 26, 2004, Dr. Kraft corrected his August 5, 2004, history, to the effect that the employee was walking up stairs, not down, at the time of his July 11, 2004, injury.

 

On August 30, 2004, the employee filed a medical request, asserting in part entitlement to payment of medical bills and authorization for the surgery recommended by Dr. Kraft.   Later that month, on September 28, 2004, the employee underwent that surgery by Dr. Kraft, in the nature of an arthroscopic  partial medial meniscectomy.  The operative report indicated in part that A[i]nspection of the medial compartment revealed that there was a small abrasion, or grade II roughening of the medial femoral condyle@ but that the Acorresponding tibial plateau appeared to be intact.@  The Amedial meniscus appeared to have a tear and actually there was a flap which was present in the posterior horn@ of the meniscus that was subsequently Atrimmed down to good base,@ leaving the remaining meniscus smooth, stable, and unremarkable.  In a letter to the employee a month later, on October 28, 2004, having on that date discussed with the employee the etiology of his condition, Dr. Kraft opined that the meniscus tear that was surgically trimmed on September 28, 2004,

 

does have some causal relationship to the year old [sic] injury as once there is a partial meniscectomy, which has been performed you are at a little greater risk at having fraying of the remaining meniscus.  Since there is no antecedent history of recent trauma, I believe that this is more of a degenerative tear and a relation can be made back to your original injury.

 

On November 9, 2004, the employee was examined for the employer by Dr. Paul Wicklund, who reported that the employee had told him that, on July 11, 2004, Ahe was simply going up the stairs without any twisting when his left knee locked.@  It was Dr. Wicklund=s opinion that this injury constituted a superseding, intervening injury.  Dr. Wicklund noted that Dr. Kraft=s operative report on his September 28, 2004, repair of the small tear in the medial meniscus had confirmed that the employee did not have any degenerative changes at all in the medial compartment, which would indicate that there had been no ongoing problems in the medial compartment related to the employee=s earlier medial meniscal surgery in 1994.  Dr. Wicklund opined further that the removal of part of the employee=s medial meniscus in 1994 did not put the employee=s left knee at any increased risk of further injury and that neither the injury to that knee on October 13, 1994, nor the injury to that knee on February 22, 1995, was a substantial contributing factor in the employee=s need for surgery in September 2004.  Dr. Wicklund=s diagnosis was of a partial right anterior cruciate ligament tear and an entirely new left medial meniscus tear, subsequently treated surgically with a good result and due entirely to the nonwork incident on July 11, 2004, notwithstanding the permanency of the employee=s October 1994 injury for which the employee had already been compensated.  Dr. Wicklund concluded also that the employee=s low back injury on September 16, 2002, neither contributed to the employee=s July 2004 knee injury nor was aggravated by that injury.  He concluded further that the employee had not been totally unable to work from and after July 14, 2004, that he could return to full-time work subject to restrictions related only to his low back injury and not to either of his knees, that he had reached maximum medical improvement from his October 13, 1994, knee injury and all subsequent injuries, and that he required no further medical care related to his July 2004 knee injury.

 

On December 1, 2004, the employee amended his medical request, seeking payment for his left knee surgery.

 

In deposition testimony on February 22, 2005, Dr. Wicklund essentially reiterated the opinions that he had asserted in his November 9, 2004, report, with a few additions.  The employee had reported and been treated for eight right knee injuries from 1994 to 2001, and Dr. Wicklund testified, over objection on foundational grounds, that he thought Asomeone that would have had a problem with his left knee would have mentioned it while he was there having his right knee examined.@  He testified further that a Apopping@ in the knee with squatting was not necessarily indicative of torn cartilage and that not every torn meniscus treated arthroscopically results in eventual further surgery on that knee.  Dr. Wicklund also testified that flap tears, such as that removed in the employee=s September 2004 surgery and which are vertically oriented on the meniscus, are almost always traumatically caused, whereas other, horizontally oriented tears are more possibly degenerative in origin.  He testified that the thickest portion of a medial meniscus is about 4.5 millimeters thick and noted that this thickest edge of the employee=s meniscus was not trimmed in either of the employee=s left knee surgeries, only the tapered and thinner edge.  He opined that it would be very unlikely that someone who had had only .5 to .8 grams of meniscal tissue removed, such as the employee did in his November 1994 surgery, would go on to have any significant degenerative problems.  He noted that, according to Dr. Kraft=s report of the September 2004 knee surgery, the articular surface of the femur appeared roughened while the articular surface of the tibia appeared smooth, suggesting that this was an indication that the two surfaces had not been rubbing together for any period of time at the time of the 2004 injury - - i.e., a further indication that there was no long-term, ten-year degenerative abrasion in the knee following the employee=s November 1994 surgery.  Dr. Wicklund did acknowledge on cross examination, however, that, in reaching this conclusion, he had relied on only the post-operative reports of Dr. Kraft and had not looked himself at any arthroscopic photographs taken at the time of the 2004 surgery and, similarly, that he had relied on the radiologists= reports of the employee=s MRI scans and had not reviewed the MRI films themselves.  Counsel for the employer asserted that he had never received in discovery either the referenced photographs or certain medical records documenting evidence of chondromalacia prior to the July 2004 injury, both of which counsel for the employee had referenced in his cross-examination of Dr. Wicklund.  He asked that he and the doctor be shown that evidence, but counsel for the employee was unable or unwilling to produce it.  Finally, Dr. Wicklund testified that, whereas Dr. Kraft had advised the employee on October 28, 2004, that his partial meniscectomy in 1994 had put him at Aa little greater risk of having fraying of the remaining meniscus,@ the employee=s surgery in 2004 was to correct a flap tear in the employee=s meniscus, not a degenerative Afraying@ of that meniscus.

 

The matter came on for hearing on March 2, 2005.  The parties stipulated at hearing to work-related injuries on October 13, 1994, February 22, 1995, March 9, 1995, August 21, 1995, April 14, 1996, September 7, 1996, May 20, 1998, August 24, 2000, March 1, 2001, March 24, 2002, and September 16, 2002.  They stipulated also that the employee=s September 28, 2004, arthroscopic surgery was reasonable and necessary, and the employer agreed to pay all medical expenses related to that surgery should the employee=s work injuries on July 14, 1994, and subsequent dates be determined to be substantial contributing factors in the need for that surgery.  That causal relationship was the principal issue at hearing.  The employee testified at hearing in part that he specifically elected not to have his entire medial meniscus removed at his November 1994 surgery, as Dr. Kraft had recommended, because he wanted to avoid complications experienced by his father, who had undergone such a procedure years earlier.  He testified further that, subsequent to his November 1994 surgery, he had only self-modified his work as a firefighter in hopes of retaining his standing commensurate pay as an unrestricted firefighter.  He testified that he routinely assumed easier positions and tasks that were less likely to aggravate his knee, adding that the other firefighters realized his problem and helped as much as possible to work around it.  The record was left open pending post-hearing submission of certain intervention motions and deposition testimony from Dr. Kraft.

 

Dr. Kraft testified by deposition on March 30, 2005, essentially reiterating opinions asserted earlier in the medical record.  Dr. Kraft testified also in part, however, that the employee had reported to him in August of 2004 that his left knee pain Aseemed to start@ with the stair-climbing incident on July 11, 2004, at which time Ahe noted some pain and crackling when he was twisting.@  The doctor indicated that the photographs that he had taken arthroscopically in the course of the September 28, 2004, surgery Aindicated that he did have some very mild degenerative changes of the articular cartilage over [the medial meniscal] area indicating that this had been going on for some time.@  Dr. Kraft subsequently testified, however, that the Grade II roughening on the employee=s medial femoral condyle, observed at the time of the latter surgery, was not degenerative and that the mechanism of the July 11, 2004, injury that compelled that surgery was a twisting injury, the knee having been rendered weaker and Aan area of risk@ by the October 1994 work injury.  He testified that the mild crepitance that he referenced in February of 1995 was Ato some degree@ suggestive of a disease process which Acould be causally related to the meniscal pathology which was present@ and that certain chondromalacia changes observed ten years later in the course of the September 2004 surgery could mean Athat there=s some softening and some irregularity of the surface overlying that meniscus which [ha]s indicated that the meniscus has been rubbing on that area.@  The doctor subsequently testified also, however, that the chondromalacia that he had diagnosed in February 1995 Awas basically from disuse atrophy of [the employee=s] quadriceps, and really does not have a whole lot to do with [the employee=s] meniscus@ and therefore was not medically significant in the case.  Dr. Kraft testified further that, contrary to the opinion of Dr. Wicklund, sometimes meniscal problems will cause more rubbing on the femur than on the tibia, that condyle abrasions and chondromalacia changes on them are not always mirroring each other.  Ultimately, it was Dr. Kraft=s opinion that the employee=s knee Ahas not the same stability that he had had before,@ that Ahe has no longer the cushioning effect of that full meniscus.  That renders increased strain on the remaining meniscus and also on the surfaces of the knee joint.@  Dr. Kraft did indicate that he had not seen the report of the employee=s August 2003 functional capacities evaluation and was unaware that the employee had reported to the evaluators that he did not have any functional problems with his knees.

 

The record closed on May 2, 2005, and by findings and order filed May 3, 2005, the compensation judge concluded in part that the employee had failed to prove that any of his right knee, low back, or left knee work injuries were substantial contributing factors in the employee=s need for left knee surgery on September 28, 2004.  The employee appeals.

 

STANDARD OF REVIEW

 

In reviewing cases on appeal, the Workers= Compensation Court of Appeals must determine whether Athe 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 (1992).  Substantial evidence supports the findings if, in the context of the entire record, Athey 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, A[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 Food 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, Aunless 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.

 

DECISION

 

The compensation judge found that neither the employee=s left knee injury on October 13, 1994, nor either of his left knee injuries between February 1, 1995, and July 11, 2004, nor any of his low back or right knee injuries during that same period was a substantial contributing factor in the employee=s need for left knee surgery on September 28, 2004.  The employee contends first that the judge=s decision was made in reliance on a medical opinion of insufficient foundation.  He argues that Dr. Wicklund, on whose opinion the judge appears to have relied, acknowledged that he did not personally observe the MRI scans themselves of the employee=s 1994 surgery, that he did not see any photographs of the employee=s knee taken arthroscopically in the context of the employee=s 2004 surgery, and that he was unaware that the employee had been diagnosed with chondromalacia.  The employee contends also that, particularly in light of the fact that his left knee has been rated with permanent partial disability,  the judge=s conclusion constitutes a finding that the employee=s September 2004 injury at home was a superseding intervening cause of the employee=s need for further surgery and that the judge misapplied the law applicable to that context.  He argues specifically that the burden of proof applicable in a superseding intervening cause defense is on the employer and insurer, that the employer in this case never presumed to assume that burden, and that, even if it had, it should not have prevailed, in light of the employee=s consistent testimony that his left knee symptoms continued right up to the time of the September 2004 injury.  We are not persuaded.

 

1.  Choice of Medical Opinion

 

Near the beginning of the section of his brief on appeal addressing this issue, the employee asserts that A[t]he testimony of the Employee=s treating doctor, Dr. Kraft, was submitted post-Hearing and it does not appear from a review of the Findings or Memorandum that she even read the deposition testimony of the treating surgeon let alone considered it in forming her decision.@  In his reply brief, having quoted certain specific conclusions of the judge in her memorandum, the employee asserts again,

 

As the court can see, the compensation judge claims to have cited specific passages of both physicians= testimony in support of these findings.  A review of the cited testimony, however, does not support the compensation judge=s position.  Based on the cited passages, the compensation judge could not have come to the conclusion found in her memorandum.@

 

We do not agree.  While mentioning neither Dr. Kraft nor Dr. Wicklund by name in her decision, the judge does clearly reference in her memorandum multiple specific pages from both of their depositions,  nor are those cited passages, particularly when viewed in their broader contexts, unsupportive of the conclusions reached by the judge.  It is apparent to us that the judge both read the depositions of both doctors and considered them in forming her decision.

 

With regard to his specific foundational challenges to Dr. Wicklund=s opinion, the employee argues that this case is unique Ain that Dr. Wicklund himself agreed that reviewing surgical photographs (which are 100% accurate) was preferable to reviewing MRI scans (it should be noted that Dr. Wicklund did not even review the scans either but rather read another=s interpretation).@  We conclude, however, that the doctor=s reliance on the treating surgeon=s surgical report and the radiologist=s MRI reports instead of on his own personal observation of arthroscopic photographs that may have been taken in the course of surgery or at least on the actual MRI films themselves was not disqualifying of his opinion as a medical expert.  Dr. Wicklund was entitled to rely on the physical observations of other qualified medical professionals, and his ultimate causation report and opinion, in reliance on the accuracy of those observations, is detailed and thorough.  The employee argues further that Dr. Wicklund Agave no indication that he was aware of the mechanism of the 1994 injury.@  We conclude, however, that, while, in addition to the mechanism of the 2004 injury, the radiological and operative findings of the 1994 injury might be critical, the mechanism of the 1994 injury is not critically relevant to the causation of the 2004 injury.  Nor is it dispositive, as suggested by the employee, that Dr. Wicklund may have been unaware of Dr. Kraft=s 1995 diagnosis of chondromalacia, in that Dr. Kraft himself later testified that the employee=s Achondromalacia of 1995 was basically from disuse atrophy of [the employee=s] quadriceps,@ did not have much to do with the employee=s meniscus, and really wasn=t medically significant in this case.  Concluding that Dr. Wicklund did not improperly rely on the operative reports of Dr. Kraft and the MRI reports of the attending radiologists rather than on arthroscopic photographs and MRI films themselves, and concluding that his unawareness of Dr. Kraft=s 1995 chondromalacia diagnosis was essentially moot under the facts of this case, we will not conclude that Dr. Wicklund=s otherwise detailed opinions were without adequate foundation to be relied upon by the compensation judge.  See Nord v. City of Cook, 360 N.W.2d 337, 342-43, 37 W.C.D. 364, 372-73 (Minn. 1985) (a 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).

 

2.  Burden of Proof and Medical Causation

 

It is true that Dr. Wicklund characterized the employee=s injury at home on July 11, 2004 as a Asuperseding, intervening injury@ and that, as indicated in her initial, pre-opening-argument summary of the case, the compensation judge indicated that Athe employer . . . takes the position that [the employee=s recent left knee] surgery is not related to the admitted work injury, and that also in fact there was a super[s]eding, intervening cause.@  Neither party referenced by name this theory of the case in its opening statement, however,^[1] and we do not agree that the judge=s conclusion constitutes a finding that the injury at issue here falls within that category or that she applied that legal theory.  Neither the mere fact that the judge appears to generally credit Dr. Wicklund=s opinions over those of Dr. Kraft nor the mere fact that the employee has been rated with and compensated for a permanent partial disability related to his left knee would compel such a conclusion.

 

A compensation judge is free to accept a portion of an expert's opinion while rejecting other portions, Johnson v. L. S. Black Constr. Co., slip op. (W.C.C.A. Aug. 18, 1994), citing City of Minnetonka v. Carlson, 298 N.W.2d 763, 767 (Minn. 1980) (a factfinder generally may accept all or only part of any witness's testimony), and Dr. Wicklund=s voluntary use of the legal term of art in the context of his medical opinion is in no way dispositive of the judge=s theory of the case, given especially that the judge never once used the term in her decision.  Moreover, notwithstanding the fact that the employee had been paid permanent partial disability benefits related to his 1994 left knee injury and consequent surgery, it is clear from the judge=s memorandum that she understood the causal relationship between that injury and the employee=s 2004 injury at home to have been severed long before July 2004.  In order for the judge to have been applying an implied superseding intervening cause analysis, and thereby shifting the burden of proof to the defending employer, the judge would need to have been viewing the employee=s left knee problems as continuing substantially right up to the time of the July 2004 injury.  This she did not do, as is evident in her crediting the absence of complaints in the written medical record over the testimony of the employee that residual problems in his left knee were substantial and ongoing in 2004:

 

There is little doubt that if the employee had, in fact, had any significant problems with his left knee he would have reported them immediately and seen a doctor.  He was very aware of the need to report changes in his condition caused by work activities as soon as possible.  Also noteworthy are references in the medical records to the lack of left knee problems.

 

The judge=s memorandum (underscoring added).  Nor would it have been unreasonable for the compensation judge to conclude that the employee=s suggestion that he had substantial ongoing left knee pain but refrained from complaining of it in order to maintain his employment status does not reconcile with his evident readiness to complain of and be treated for right knee problems on a regular basis.  Nor was it unreasonable for Dr. Wicklund and the compensation judge to presume that complaints of substantial left knee pain would naturally have come out in examinations related to disabling right knee and low back pain.  The judge=s decision here was not unreasonable, and therefore we affirm it.  See  Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.