The self-insured employer appeals from the compensation judge’s application of principles of res judicata and from his awards of wage replacement and medical benefits, and the employee cross-appeals from the judge’s denial of the employee’s request for surgery.  We affirm.

The first reference to Jerry Keppers’ right knee in his medical records is on August 24, 1999, when he was seen regarding pain that he had felt in the knee during a night of dancing, after a “pop” that his sister had heard at the time.  An MRI scan was conducted on August 27, 1999, and was read as normal, except in that the posterior horns of the lateral and medial menisci revealed some “lamellation” and that of the latter also appeared somewhat frayed, although no clear-cut tear was identified.  Later that same year, on September 27, 1999, Mr. Keppers tore his right quadriceps tendon when he fell at home, following which he underwent immediate open surgical repair.  He retore the same right quadriceps tendon on November 12, 1999, when he slipped and fell on some steps, again at home.  These injuries resulted in several surgeries in late 1999 and the spring of 2000, several of them in an attempt to mitigate a staph infection complicated by Mr. Keppers’ diabetes.  Medical records four years later, in May of 2004, indicate that Mr. Keppers sustained an abrasion of his right knee in that year as well, which seemed, again perhaps due to his diabetes, to be taking a long time to heal.

Mr. Keppers sought treatment for his right knee again in November of 2005, after it “popped out and went back in” while he was in the process of mowing his lawn.  After physical therapy and injection treatment apparently proved ineffective, on December 2, 2005, orthopedic surgeon Dr. Everett Hughes performed arthroscopic surgery on the knee, which resulted in debridement of the medial femoral condyle, removal of multiple loose chondral fragments, and debridement of the medial and lateral menisci.  According to the operative summary, the arthroscopy also revealed

On July 20, 2006, Mr. Keppers [the employee] sustained a work-related injury again to his right knee when he tripped over a pallet and fell and landed directly on the front of the knee, in the course of his work making leather boots with Red Wing Shoe Company [the employer], for whom he had apparently worked for over eighteen years.  Subsequent to his injury, the employee was restricted from working for twenty-four hours and was then instructed by his doctor for a month to “take it easy.”  On August 23, 2006, about a month after the injury, the employee was terminated by the employer, evidently for failure to adhere to appropriate call-in protocols.  The employee had been forty-six years old on the date of his injury and had been earning a weekly wage of $558.00.  The employer, which was self-insured against workers’ compensation liability at the time, admitted liability for the injury and commenced payment of various benefits.

On December 13, 2006, the employee was examined for the employer by orthopedic surgeon Dr. Richard Strand.  In his report on December 19, 2006, Dr. Strand diagnosed contusion of the right knee anterior extensor mechanism, status post extensive surgeries for quadriceps rupture and degenerative arthritis of the right knee, together with degenerative arthrosis of the right knee, status post septic knee arthritis, status post arthroscopic decompression.  Dr. Strand opined that the underlying cause of the contusion was the employee’s fall on July 20, 2006, that the degenerative arthritis was due to apparently pre-existing malalignment of his patella together with his subsequent quadriceps tendon rupture and associated surgeries for infections, and that the underlying cause of the arthrosis was the employee’s age, size, weight, previous severe injuries to his extensor mechanism, and septic arthritis in the knee.  The doctor opined that the employee’s contusion work injury was not the cause of his current complaints, which the doctor concluded were due to extensive pre-existing disease and were being magnified.  It was the doctor’s opinion that treatment for the contusion of the employee’s patella was reasonable and necessary at the time but that that injury was now healed and ongoing problems were not work related.  Dr. Strand indicated that in his opinion the employee was not in need of any further treatment for his work-related contusion, although, regardless of causation, he might eventually need treatment for his degenerative arthritis.  The doctor opined that the employee was not at the time of the examination a candidate for total knee replacement, there being no evidence that such surgery would relieve his knee disease, and given the employee’s severe cardiac disease, diabetic neuropathy, and history of knee infection.  Concluding that the employee was “far more functional than he says he is,” Dr. Strand indicated that the only restrictions required by the employee would be restrictions on extended standing, climbing, stooping, and walking, related to the employee’s degenerative arthritis.  Dr. Strand concluded that the employee had already reached maximum medical improvement [MMI] with regard to his July 20, 2006, work injury, probably within about six weeks of the incident.  Finally, the doctor concluded that the employee’s July 20, 2006, work injury was a temporary aggravation of a pre-existing condition and that the employee had not sustained any permanent partial disability as a result of it.

On June 25, 2007, with symptoms persisting in the employee’s right knee, the employee’s surgeon, Dr. Hughes, issued a narrative report to the employee’s attorney.  In his report, the doctor recommended a diagnostic arthroscopy of the employee’s right knee, the employee being unable to have an MRI scan, given the placement of a cardiac defibrillator in his chest.  Noting that the employee “had essentially complete resolution of his symptoms” following his previous arthroscopy in 2005, Dr. Hughes went on to indicate that, in his opinion, the employee’s current right knee condition, need for restrictions, and need for the recommended surgery were all directly related to his July 20, 2006, work injury.

On August 16, 2007, the employee filed a claim petition, alleging entitlement to various benefits consequent to his July 20, 2006, work injury, including temporary total disability compensation, rehabilitation services, and the arthroscopic surgery recommended by Dr. Hughes.

On December 17, 2007, Dr. Strand issued to the employer’s attorney another evaluation of the employee’s medical condition, based on a review of his earlier examination findings together with subsequent and additional medical records.  In his evaluation, Dr. Strand opined that the underlying cause of the employee’s current knee condition was totally unrelated to his work-related contusion of July 20, 2006.  He concluded further that there was no evidence that the employee suffered any permanent partial disability as a result of his work injury, and he did not believe that the employee was at that time in need of any further medical care or treatment related to that injury.  Moreover, it was his opinion, finally, that the repeated arthroscopic diagnostics and debridement that the employee had undergone were “not helpful” and that the employee was

The matter eventually came on for hearing on January 4, 2008.  By findings and order filed March 3, 2008, the compensation judge concluded in part that the employee’s 2006 work injury was “a substantial aggravating and contributing cause of” his ongoing right knee problems and that the proposed arthroscopic surgical procedure was reasonable and necessary to cure or relieve the effects of that injury.  The judge denied, however, the employee’s request for temporary total disability benefits continuing from January 8, 2007, because the employee had not made a diligent effort to find employment within his restrictions.  A rehabilitation consultation was ordered, and on April 8, 2008, the employee underwent the consultation with QRC Bill Rutenbeck and was found to be a qualified employee for rehabilitation assistance.  On that same date, Dr. Hughes restricted the employee from working until after his surgery, including a possible anterior cruciate ligament [ACL] reconstruction.

On April 10, 2008, Dr. Hughes performed the recommended surgery - - a right knee arthroscopy, partial medial meniscectomy, and debridement of notch scar tissue.  In his post-operative report, Dr. Hughes noted in part that there were grade 3 and 4 changes to the medial femoral condyle, that the medial meniscus was torn, and that the ACL was observed to be partially torn.  Dr. Hughes indicated that he had performed only the meniscectomy and not addressed the ACL, because it was deemed unlikely to benefit from any type of reconstruction.

Subsequent to his surgery, the employee was restricted from all work, and on April 14, 2008, he commenced physical therapy.  He apparently did not have a good result from his surgery, and his symptoms actually seemed to get worse with the therapy.  On May 15, 2008, QRC Rutenbeck wrote to the employer’s claims representative, Phil Rendina, advising him that he understood from the employee that Dr. Hughes had implied that the employee might eventually require a total knee replacement.  On May 20, 2008, Dr. Hughes released the employee to return to work at only sedentary employment, noting that he had “[q]uite significant degenerative changes to his knee with problems with persistent pain and instability.”  On June 4, 2008, QRC Rutenbeck administered some vocational testing, and attention was given to developing an appropriate vocational plan.  No formal job search was immediately commenced, however, apparently in light of the possibility of further surgery in the near future.

On August 6, 2008, the employee’s physical therapist noted “an open area on the [right] kneecap itself,” about the size of a dime, that was “through the layers of the skin” and “actually deep into the fascial tissue and nearly expos[ing] the tendon.”  The therapist had a physician and some wound specialists examine the lesion, and it was treated with a dressing and some ointment.  With injection therapy and physical therapy proving essentially ineffective in relieving the employee’s pain, on August 12, 2008, Dr. Hughes formally recommended a total knee replacement.  The doctor noted on that date that the employee “does have an area of difficult healing from an injury to the anterior aspect of his knee, but there is no distinct infection going on.”  Upon this surgical recommendation by Dr. Hughes, all vocational planning was put on hold.

On August 22, 2008, the employee was seen by his primary doctor, Dr. Karl Molenaar, apparently with regard to Dr. Hughes’ surgical recommendation.  Dr. Molenaar noted that the employee had “bumped [his knee] a number of months ago and unfortunately he has developed an ulcer in this area.”  The doctor diagnosed “[d]iabetic wound” and recommended that the employee “cannot have knee surgery while this is an open wound.”  On August 27, 2008, the employee saw in consultation Dr. Thomas Blee, on referral from Dr. Molenaar.  Dr. Blee reported “a hematoma and an open sore on the kneecap,” caused by an “injury about six months ago where he fe[l]l on his right kneecap” and “developed a hematoma and an open sore on the kneecap.”  Dr. Blee noted further, “Visible at the base of the wound is the bursa over the knee joint,” concluding, “This is going to take a long time to heal.”  The infection was still worsening on September 5, 2008, and Dr. Molenaar admitted the employee to the hospital, where Dr. Hughes performed on that date a right prepatellar bursectomy, with irrigation, debridement, and closure of the anterior knee wound.

The employee was examined another time by Dr. Strand on September 24, 2008.  In his report on that date, Dr. Strand reiterated his opinion that the employee’s July 20, 2006, contusion work injury was not in any way related to his current right knee problems.  He opined also that, given his cardiac and diabetic neuropathy conditions, the employee was not a candidate for a total knee arthroplasty.  The doctor then went on to state that the

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.

At Finding 3, the compensation judge reported the following in reference to the prior hearing in this matter, held on January 4, 2008:

A decision as to an employee’s entitlement to temporary wage replacement and/or medical benefits for a particular period of time is not res judicata with regard to his or her entitlement to such benefits for a different period of time and/or treatment.  Evidence and defenses will differ with each new period of wage replacement and each new requested treatment, as here they do.  The three reports of Dr. Strand upon which the employer based its current defense - - made in December 2006, December 2007, and September 2008 - - did repeatedly allege that the employee’s 2006 work injury was a temporary one that had fully resolved, most likely within six weeks after the injury - - notwithstanding the compensation judge’s March 2008 finding that the injury was still a substantial cause of the employee’s “ongoing” knee problems at that time.  However, other defenses to the employee’s claim that his work injury has continued to be “ongoing,” during subsequent benefit periods and requiring different treatment, have also been asserted.  Hence, the doctrine of res judicata has no application here, since neither the specific issues of the 2008 proceeding nor the doctrine itself was at issue at the 2009 proceeding.

That said, however, and notwithstanding the judge’s brief reference to the doctrine, in a single sentence, in his memorandum, we find nothing in any of the compensation judge’s August 2009 findings or orders to suggest that the judge’s conclusions in this recent proceeding, regarding total knee replacement surgery and wage replacement continuing since October 30, 2008, were dictated by any res judicata effect of his March 2008 conclusions in the previous proceeding, regarding arthroscopic surgery, rehabilitation benefits, and wage replacement prior to that time.

At Finding 10 the compensation judge concluded that the employee’s July 2006 work injury was a “substantial aggravating and contributing” cause of the employee’s ongoing right knee problems and need for total knee replacement, and at Findings 14 and 15 he concluded that the employee was therefore entitled to temporary total and temporary partial disability benefits.  In addition to finding the judge’s decision erroneous as a matter of law, as addressed above, the employer contends that these conclusions of the judge as to causation are unsupported by substantial evidence.  The employer argues that the employee’s work-related injury of July 2006 was completely resolved with his April 2008 arthroscopic surgery and that the contrary opinions of Dr. Hughes, on which the judge relied, were “flawed, inaccurate and deficient,” contrary to those of Dr. Strand.  We are not persuaded.

The employer contends that the employee’s work injury was completely and permanently resolved with the April 2008 repair of his right medial meniscus tear, arguing that the torn ACL evident during the arthroscopy was a condition pre-existing the work injury.  We note, however, that the only abnormality reported in the most recent pre-injury reference to the employee’s ACL, in Dr. Hughes’ December 2, 2005, arthroscopic operative report, is only some fraying that was completely resolved by simple debridement, whereas the most recent post-injury reference, in Dr. Hughes’ April 10, 2008, arthroscopic operative report, notes that “the ACL was observed to be partially torn.”  Moreover, in his November 20, 2008, narrative report to the employee’s attorney, Dr. Hughes expressly opined that this condition was directly related causally to the employee’s July 20, 2006, work injury.  The employer has argued that the opinions of Dr. Hughes have failed to take into consideration the doctor’s own prior operative reports, which the employer argues showed significant preexisting degenerative changes in the employee’s knee, including ACL involvement.  The record documents, however, a clear change in the ACL, from frayed pre-injury to torn post-injury, and we find due consideration for that record in Dr. Hughes’ opinion that the torn ACL has led to an instability that has in turn been “hastening and accelerating the degenerative changes that [the employee] had already experienced.”  The employer argues that Dr. Hughes’ opinions fail also, contrary to the opinions of Dr. Strand, to take into consideration, as possible causes of the employee’s current condition, the employee’s morbid obesity, his history of smoking, his multiple surgical interventions on the left knee, his diabetic joint neuropathy, his ten-year history of significant joint degeneration and arthritis, and his ten prior right knee surgical interventions.  Dr. Hughes addressed these considerations also in the November 20, 2008, narrative report in which he reiterated his recommendation of total knee surgery.  We conclude that it was not unreasonable for the compensation judge to rely on the opinion of Dr. Hughes and that the judge’s conclusion on the issue of causation is not therefore or otherwise 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) (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); Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.

At Finding 7, the compensation judge described the infection in the employee’s right knee for which the employee had been treated since August 2008, concluding that “[t]here is little evidence that the infection has been cured.”  At Finding 11, the judge went on to conclude that the total knee replacement requested by the employee - - while causally related to the work injury, as found in Finding 10 - - was not currently reasonable and necessary, because “[t]he chronic infection in the right knee makes the procedure too dangerous at the present time.”  In his memorandum, the compensation judge explained that he was “persuaded by the opinion of Dr. Strand” in reaching this conclusion.  The employee contends that the judge’s conclusion is clearly erroneous and unsupported by substantial evidence, in that the report of Dr. Strand, upon which the judge relied, had neither the necessary evidentiary support nor the requisite factual foundation to be relied upon, leaving Dr. Hughes’s opinion recommending the surgery uncontroverted.  We are not persuaded.

In his brief, the employee’s only argument as to the sufficiency of evidentiary support for Dr. Strand’s opinion is that the doctor’s opinion was based on a conclusion that the employee’s work injury was only temporary and has already resolved, which the employee contends is contrary to the law of the case.  As the employee observes, this conclusion by Dr. Strand as to the duration of the employee’s injury constitutes an opinion that the employee’s work injury is no longer causally related to his current condition.  Without explanation, however, the employee appears to ignore the fact that the judge concluded expressly at Finding 10 - - in the employee’s own favor - - that the employee’s work injury was causally related to his need for knee replacement surgery.  The judge’s denial of knee replacement surgery was based not on a conclusion that such surgery was not causally related to the work injury but on a conclusion that such surgery was not reasonable and necessary “at the present time.”  Dr. Strand’s opinion as to causation is not relevant to the issue of whether the requested surgery is currently reasonable and necessary in light of the employee’s chronic infection.  Nor do we find Dr. Strand’s opinion insufficient on foundational grounds to have been relied on to the extent that it was.  In that the employee has not addressed, either foundationally or in terms of substantial evidence, the actual basis for the judge’s denial of his request for total knee replacement, we will not reverse the judge’s denial of the surgery, which we find reasonably supported on its expressed basis in the medical opinion of Dr. Strand.  See Nord, 360 N.W.2d at 342-43, 37 W.C.D. at 372-73; Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.