The employer and insurer appeal from the compensation judge’s determination that the employee sustained work-related injuries to his left hand and wrist in 1978 and to his right hand and wrist in 1979, from the judge’s findings that the employee provided statutory notice and that his claims were not barred by the statute of limitations, from the judge’s award of wage loss benefits continuing from January 1, 1982, and from the judge’s failure to allow apportionment or a set off against the employee’s subsequent settlement for a work-related knee injury.  The employee cross-appeals from the judge’s denial of wage loss benefits for the years 1990, 1991, and 1992.  We affirm.

Frank Myers [the employee] played professional football as an offensive tackle with the Minnesota Vikings Football Club, Inc. [the employer], during the 1978, 1979, and 1980 football seasons.  Prior to his employment with the employer, he played for a short time with the Baltimore Colts, and was a four-year starter at Texas A & M University from 1974 to 1978.  In 1974, while playing college football, the employee had sustained an injury to his left knee that required surgery and removal of some cartilage.  Despite the injury, he successfully completed his college playing career and later passed the necessary physical examinations required by the Baltimore Colts and the employer.

While the employee was employed by the employer, the employer’s “team physician” was orthopedist Dr. Donald Lannin.  The employer also employed a training staff led by trainer Fred Zamberletti.  According to the training room daily treatment records kept during the employee’s tenure with the employer, the employee was treated fairly regularly for groin strains and left hamstring complaints.  The employer’s records do not reflect any history or complaints of right hand and wrist problems during 1978, 1979, or 1980.^[1]  On December 7, 1979, the employee fell during a practice  session and twisted his left wrist.  He was examined by Dr. Lannin, who obtained an x-ray of the wrist.  The x-ray revealed no fractures or bony abnormality, and the doctor recommended wrist taping and released the employee to continue playing.  Team medical records reflect no further treatment for the employee’s left wrist.

On July 30, 1980, the employee was examined by Dr. Lannin to begin the 1980 season.  The employee reported no left knee or other orthopedic complaints, and he mentioned that he had been playing football during the off-season.  Dr. Lannin concluded that the employee had a 15% permanent partial disability of the left lower extremity because of his old knee injury, but he cleared the employee for training camp.

On August 7, 1980, while practicing in training camp, the employee twisted his left knee at the point of his old injury.  He was thereafter followed in the training room and by Dr. Lannin on a regular basis.  The employee further aggravated his left knee on August 24, 1980, and underwent an arthrogram of the knee the following day.  In an office note dated September 17, 1980, Dr. Lannin reported that the employee was running well in practice and carrying out all of the regular drills.  Dr. Lannin concluded that the employee had reached maximum medical improvement and that his knee had returned to the level it was before his twisting injury the previous month, and he released the employee to play football without restrictions.

The employee was seen for a second opinion by Dr. E. Harvey O’Phelan on September 19, 1980.  Dr. O’Phelan concluded that the employee had sustained a sprain of the medial collateral ligament superimposed on early degenerative changes of the medial femoral condyle secondary to his initial knee injury in 1974.  He concluded the employee could continue to play professional football with minimal soreness “which eventually should subside without serious disability.”

On or about October 2, 1980, the employee was informed that the employer had placed him on waivers.

The employee was examined by orthopedic surgeon Dr. James Elbaor in Arlington, Texas, on November 14, 1980.  Dr. Elbaor diagnosed an internal derangement of the left knee, a probable cruciate injury, and possible chondromalacia.  On December 27, 1980, Dr. Elbaor hospitalized the employee for arthroscopic exploration of the left knee.

On March 2, 1981, the employee consulted Dr. Elbaor regarding a thickening in the right long finger base, which he said he had just noticed developing.  Dr. Elbaor thought that it “look[ed] like an early dupuytrens contracture.”^[2]  He noted some early development in the left long finger base as well.  The employee told the doctor that he injured it frequently playing football.  The doctor did not think that surgery was indicated, and he doubted that a steroid injection would help.

On August 10, 1981, the employee was seen for another opinion regarding his knee condition by orthopedist Dr. James Butler, in Houston, Texas.  In the history provided to Dr. Butler, the employee described a third injury to his knee on September 18, 1980, while pass blocking during practice.  The employee stated that his knee “gave way,” causing him to fall down.  The employee told Dr Butler that he had “not been able to participate in his usual fashion because the leg feels like it is going out from under him.”  Dr. Butler concluded that the employee had an abnormal drawer sign on physical examination, and he supposed that the true status of the employee’s knee was much worse than what was demonstrated on routine physical examination.  He suggested that the employee engage in an intensive exercise program for four to six weeks to see if he would be able to return to playing football at the professional level.

In a March 15, 1983, letter to the employee’s attorney, Dr. Elbaor related the employee’s left knee condition to his work injuries and rated permanent partial disability at 46 to 48% of the leg.

On about July 27, 1983, the employee filed a claim petition, seeking temporary total and/or temporary partial disability benefits continuing from September 21, 1980, and compensation for permanent partial disability as rated by Dr. Elbaor, all related to his left knee injuries of August 7, August 24, and September 18, 1980.  The employer, self-insured for its workers’ compensation liability on the dates claimed, admitted the employee’s injuries but denied that the employee was entitled to the benefits claimed.

The employee was examined at the request of the employer by Dr. Larry Stern on October 18, 1984.  The employee informed Dr. Stern of his arthroscopic procedures in November and December of 1980, and he advised Dr. Stern that in 1981 he had begun running again for conditioning but that his knee had gotten worse and would swell.  He told Dr. Stern that he had then had a third arthroscopic surgery, that in 1982 he had had no luck getting a football try-out, and that in 1983 he had had a try-out for a USFL team “but the left knee flunked the physical.”  Dr. Stern diagnosed “status post left knee medial meniscectomy with subsequent degenerative changes of medical compartment” and rated the employee’s permanent partial disability at 23% of his left leg.

The parties agreed to a settlement of the employee’s claims in late 1984.  The employer agreed to pay 77 weeks of benefits in settlement of the employee’s claim for permanent partial disability to the extent of 46 to 48% of the leg and an additional payment of $40,598.00 in return for full, final, and complete settlement of the employee’s claims for all remaining benefits provided by the Workers’ Compensation Act, with the exception of reasonable and necessary medical treatment for the employee’s left knee.  An Award on Stipulation was issued by a compensation judge on January 22, 1985.

On March 7, 2003, just over eighteen years later, the employee filed a claim petition, alleging entitlement to benefits payable by the then uninsured employer, based on an injury to his right hand in the fall of 1978 and to his left hand and wrist on December 7, 1979.  A year later, on May 25, 2004, the employee amended his petition to allege his claim against the employer and the insurer on the risk on the dates of his alleged injuries, Employer’s Insurance of Wausau.  The employer and insurer denied liability for the alleged injuries, asserting in part that the employee had failed to provide notice as required by Minnesota Statutes section 176.141 and that the employee’s claims were barred by the six-year statute of limitations, Minnesota Statutes section 176.151.

On January 6, 2005, the employee was examined at the request of the employer and insurer by orthopedist Dr. Jack Kern of Fort Worth, Texas.  Dr. Kern obtained a history from the employee, reviewed medical records, performed a physical examination, issued a report, and later testified by deposition on August 22, 2006.  In the history portion of his January 6, 2005 report, Dr. Kern reported that,

Dr. Kern diagnosed “Dupuytren’s fasciitis and history of contractures, right and left hands, in the presence of injuries to both hands requiring splinting while performing as a professional football lineman, 1978 and 1979.”  He found the employee’s 1978 and December 7, 1979, injuries and necessary splinting to be a substantial contributing cause of the employee’s Dupuytren’s condition, subsequent contractures, and surgeries.  He also related the employee’s carpal tunnel releases to his Dupuytren’s condition, his splinting, and his hand injuries.  The doctor opined that the work injuries were a substantial contributing cause of the employee’s lost time from work following his surgeries and of his restrictions against performing heavy laboring activities and certain assembly-type work.  He concluded that the employee would be capable of light to medium work.  Finally, the doctor rated the employee’s permanent partial disability at 10% with regard to each hand and wrist, noting that the employee had diminished grip strength in both hands and impaired range of motion of the DIP joints of the fingers of the left hand.

On August 28, 2006, Dr. Michael Doyle, the surgeon who performed the last of the employee’s right hand surgeries in 2002, wrote to the employee’s attorney and concurred with Dr. Kern’s testimony regarding the employee’s permanent partial disability.

The employee’s claims for benefits based on his bilateral hand and wrist injuries came on for hearing before a compensation judge on September 14, 2006.  Testimony at trial was provided solely by the employee, with Dr. Kern’s testimony presented by deposition.  Documentary evidence included the employee’s tax returns and W-2 forms from 1982 to 1999, payroll records for the period February 22, 1999, to July 12, 2006, selected medical records related to the employee’s hand surgeries, and the employer’s employment file on the employee.  The parties identified the following issues for determination by the judge:  (1) whether the employee’s alleged injuries in the fall of 1978 and on December 7, 1979, arose out of and in the course of his employment with the employer; (2) whether the employee’s claims are barred based on a lack of statutory notice or by operation of the statute of limitations; (3) whether the employee is entitled to claimed temporary total and temporary partial disability benefits; (4) whether the employee’s claims are causally related to the alleged bilateral hand and wrist conditions; (5) whether the employee’s earnings after leaving the employer were an accurate reflection of his earning capacity; (6) whether the employee is entitled to claimed permanent partial disability; and (7) whether the employee’s knee injury constitutes a superseding, intervening cause of disability.

At hearing, the employee rendered testimony similar to the history that he had recounted to Dr. Kern in January of 2005.  He testified that sometime in October or November of 1978 he reported pain in his right palm to team trainer Fred Zamberletti, who made a thermoplastic cast that covered the entire palm and was affixed to his hand with tape.  He testified that thereafter he wore the splint and tape for both practice and games because the pain in his hand continued without relief.  He testified that Dr. Lannin also examined his hand while the splint and tape were being applied.  As time went by, he testified, he noticed and reported pinching from tight taping, lumps in his right palm, and some contracture of the fingers in the hand.  He testified that, when he returned to work for the employer in the fall of 1979, he underwent a physical examination and made Dr. Lannin, Mr. Zamberletti, and the rest of the staff aware of continuing problems in the hand, which he continued to tape and splint for games and practice.

The employee’s testimony with regard to his alleged December 7, 1979, injury is similarly corroborative of the history that he gave to Dr. Kern.  He testified that he fell and twisted his left wrist during practice on that date, that he saw Dr. Lannin for treatment, and that Mr. Zamberletti built a thermoplastic cast for the hand.  He testified that he subsequently developed lumps in the palm of this hand as well, immediately after he began wearing the cast.  By the end of the 1979 season, he testified, both the long finger and the pinky finger on his right hand were folding down, and he could not extend them.  He could still close his hand, he testified, but he couldn’t open it all the way, that he had a bump on his left hand but his right hand was more disabled.

Finally, the employee testified that after leaving the employer in 1980 he made efforts to obtain try-outs with other football teams but that his weight training was significantly limited due to pain in his wrists and fingers.  He testified also regarding his self-employment efforts in 1982 and 1983 and his various jobs in the banking and mortgage industries subsequent to that time.

In a Findings and Order issued November 13, 2006, the compensation judge found that the employee’s right and left hand and wrist conditions were consequences of injuries sustained in the fall of 1978 and December 7, 1979, as those injuries aggravated or accelerated the employee’s pre-disposition to Dupuytren’s contracture.  The judge concluded that the latter condition was progressive and had worsened over time, eventually requiring multiple surgeries.  He determined that the employer had proper statutory notice of both injuries and that, based on the employee’s credible testimony, the team trainer and doctor were aware on a daily basis of the employee’s medical problems.  The judge found that the employee was provided with medical attention and treatment in the form of casts and splinting and taping, and therefore he concluded that the employee’s claims are not barred by the statute of limitations.  The judge also found that the employee’s job search efforts during the periods of claimed disability, except for the years 1990, 1991, and 1992, were reasonable in light of all the circumstances, including his lack of rehabilitation assistance.  He found the employee’s actual earnings to be an accurate measure of the employee’s ability to earn, and he accepted Dr. Kern’s and Dr. Doyle’s opinions regarding the employee’s permanent partial disability.  Lastly, he found that, because the employee’s bilateral hand and wrist conditions were a substantial contributing factor in the employee’s ongoing disability and wage loss from January 1, 1982, to December 14, 2005, the employee’s left knee injury does not constitute a superseding cause of the employee’s disability.  The employer and insurer appeal and the employee cross-appeals.

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 (2004).  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, 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.”  Northern States Power Co. v. Lyon Food Prods., Inc., 3204 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).

At Finding 23, the compensation judge concluded that the employer had proper notice of both the employee’s 1978 right hand and wrist injury and his December 1979 left hand and wrist injury.  The employer and insurer contend that there is no indication in any 1978 medical records, training room records, or contemporaneous correspondence that the employee advised the employer of an injury to his right hand.  Nor, they argue, did he complete or request to be completed any accident report or First Report of Injury.  With regard to the alleged left hand injury in 1979, they argue that Dr. Lannin’s report on December 7, 1979, though it mentions taping on that date, does not indicate that the employee was issued a splint, as the employee alleges, nor is there any evidence that the sprain that was being treated had anything to do with the employee’s later problems or his Dupuytren’s contracture.  And again, they argue, no First Report of Injury or incident report or corroborative correspondence is in evidence, and “[p]ayment of a medical expense by an employer,” they argue, without citation, “will have no effect on the notice requirements.”^[3]  We are not persuaded.

Minnesota Statutes section 176.141 provides, with various further limitations, that an employer must receive actual or informed notice of a work related injury no later than one hundred eighty days after the injury for any compensation to be due.  Minn. Stat. § 176.141.  The employee testified that he informed the employer’s trainer of a soreness in the palm of his right hand in the fall of 1978 and that a plastic palm splint was thereupon cast for his hand and subsequently taped to his palm during each of the games in which he played.  This testimony was consistent with details of the history that the employee had given to Dr. Kern almost two years earlier.  The employee testified also that, upon his reporting his sprained left wrist in December 1979, the team doctor prescribed splinting and taping for the remainder of the football season.  This testimony, too, is consistent with Dr. Kern’s history.  The expert medical opinions of Drs. Kern and Doyle clearly support a causal connection between the 1978 and 1979 splintings and tapings of the employee’s hands and wrists and the eventual development of the employee’s latent Dupuytren’s contracture.  With regard to the lack of any written record of any treatment for his 1978 hand problems, we would note that the training room records for 1978 and 1979 were incomplete.  The employee testified that, if you had an injury and were hurting, you would go to the trainers and tell them about it, that if you didn’t you would have been fined.  He testified that he had no control over what was written about the injuries that he reported and that he never had an opportunity to look through the training records.  No evidence was offered to rebut the employee’s testimony, and in his memorandum the compensation judge expressly found it to be “quite credible and persuasive.”  Assessment of a witness's credibility is the unique function of the trier of fact, Brennan v. Joseph G. Brennan, M.D., 425 N.W.2d 837, 839-40, 41 W.C.D. 79, 82 (Minn. 1988), and, in light of the whole record, we see no basis for challenging the judge’s finding that the employee gave proper notice of the two injuries here at issue.  Therefore we affirm that finding.  See Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.

Minnesota Statutes section 176.151 provides that “[a]ctions or proceedings” to recover workers’ compensation benefits may not generally be commenced more than six years after the date of the alleged injury.  Minn. Stat. § 176.151 (1).  Notwithstanding the fact that the employee did not file his claim petition until some twenty-five years after the second of his two alleged injuries, the compensation judge concluded at Finding 23 that the employee’s claim to compensation for both of his alleged injuries was not barred by the statute of limitations.  The judge’s finding was apparently pursuant to the supreme court’s holding in Marose v. Maislin Transport, that an employer’s payment of medical expenses associated with an injury constitutes an “action or proceeding” within the meaning of Minnesota Statutes section 176.151.  Marose v. Maislin Transp., 413 N.W.2d 507, 512, 40 W.C.D. 175, 183 (Minn. 1987).  The employer and insurer contend that the judge erred in his conclusion on this issue, arguing, contrary to the position of the employee, that the employer’s splinting and taping of the employee’s wrist sprain in 1979, found by Dr. Kern to have precipitated development of the employee’s latent Dupuytren’s contracture, was neither (1) “meaningful” treatment nor (2) treatment voluntarily provided for an admitted work injury nor (3) treatment for the particular condition here at issue, all three of which they allege are required under applicable law.^[4]  On a policy basis, finally, they argue that claims such as the employee’s - - brought twenty-five years after the alleged injury - - are precisely what the statute of limitations is designed to preclude, in that the employer’s ability to defend is inherently prejudiced by the unavailability of fresh evidence.  We are not persuaded.

While determining what constitutes medical treatment in the context of professional football may sometimes be difficult to discern, we find no basis for concluding that the taping and alleged splinting of the employee’s sprained wrist in 1979 was somehow not “meaningful” treatment, particularly in its context, nor does the case cited by the employer - - Brochu v. United States Steel Corporation - - assist in any way in defining what the employer and insurer might mean by medically “meaningful.”^[5]  See Brochu v. United States Steel Corp., 237 N.W.2d 833, 28 W.C.D. 270 (Minn. 1976).  Moreover, contrary to the aspirin furnished by a company nurse to the worker for generalized back and leg pain in the case cited by the employer and insurer, Livgard v. Cornelius Company, 308 Minn. 467, 243 N.W.2d 309, 28 W.C.D. 413 (1976), the taping and splinting treatment furnished by the employer’s medical and training staff for the employee’s sprained wrist in the case here at issue was clearly specific to an injury very reasonably proceeding directly from the employee’s specific profession, and the injury’s treatment in that manner quite reasonably implies an admission of responsibility.  Finally, we are not persuaded that, for purposes of the statute of limitations, the employee’s wrist sprain in 1979 was a different injury from the Dupuytren’s contracture condition by which he continues to be disabled.  An employer and insurer may be liable “for every natural consequence that flows from” a compensable injury.  Nelsen v. American Lutheran Church, 420 N.W.2d 588, 590-91, 40 W.C.D. 849, 852 (Minn. 1988), quoting 1 A. Larson, The Law of Workmen’s Compensation, § 13.00 (1985).  Dr. Kern testified that the treatment for the employee’s work injuries - - taping and splinting - - led to an aggravation of the Dupuytren’s contracture to which the employee was predisposed.  It was not unreasonable for the compensation judge to conclude from this evidence that the employee’s development of Dupuytren’s contracture symptoms was a “natural consequence” flowing from the employee’s work injuries, and therefore we defer to that conclusion.  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).

With regard to the employer and insurer’s policy argument, we acknowledge that the twenty-five-year interim between the employee’s injury and his claim in this case renders fresh evidence difficult to obtain - - for both parties, we would note.  However, under the statute and our case law, and under the facts of this case, we cannot but conclude that the judge’s finding on this issue - - that the statute of limitations was effectively tolled by the employee’s treatment in 1978 and 1979 - - was neither legally erroneous nor factually unreasonable, and therefore we must affirm.  See Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.

At trial, the compensation judge was asked to determine whether the employee’s left knee injury, subsequent to his alleged hand injuries, constitutes a superseding, intervening cause of his post-injury wage loss.  At Finding 22, the judge found that,

In Buford v. Ford Motor Company, this court stated that the proper test to determine whether a subsequent incident or condition is a superseding, intervening cause is the “substantial contributing cause” test.  See Buford v. Ford Motor Co., 52 W.C.D. 723, 729 (W.C.C.A. 1995).  Neither statute nor case law precisely defines what constitutes a “substantial” or “significant” contributing factor in a workers’ compensation setting.  Because each case must to a great extent stand on its own facts, no one comprehensive definition can be fashioned.  See Flowers v. Consolidated Containers Corp., 336 N.W.2d 255, 36 W.C.D. 39 (Minn. 1983).  The supreme court has indicated, however, that a “substantial” contributing cause must at least be an “appreciable” one.  Roman v. Minneapolis Street Ry., 268 Minn. 367, 380, 129 N.W.2d 550, 558, 23 W.C.D. 573, 592 (1964).  In the present case, the judge applied the proper test, and substantial evidence in the record supports his determination that the employee’s hand and wrist injuries are substantial contributing factors in the employee’s disability.

In their brief on appeal, the employer and insurer argue that the employee’s work-related knee injury remains a substantial contributing cause of the employee’s claimed wage loss and that the compensation judge erred by not allowing the employer and insurer either a credit for the amount of money that the employee received in his 1985 knee settlement or an apportionment of liability between the employee’s bilateral hand and wrist conditions and his subsequent knee injury.  We disagree.

We have carefully reviewed the transcript of the proceedings before the compensation judge, as well as the employer and insurer’s Notice of Appeal, and we can discern no reference to issues of apportionment or credit as related to the employee’s 1980 knee injury.  In his Findings and Order, the judge set forth seven specific issues of law and fact submitted to him for decision.  Issues of apportionment or credit were not among them, nor did the judge issue any findings relative to these alleged issues.  The only issue raised by the employer and insurer regarding the employee’s 1980 knee injury was whether that injury constituted a superseding intervening cause of disability - an issue fully addressed by the judge.  An issue raised for the first time on appeal is not properly before the court and will not be addressed.  Malinoski v. North American Cable Sys., slip op. (W.C.C.A. Dec. 14, 1989).  Moreover, the jurisdiction of the Workers’ Compensation Court of Appeals is “limited to the issues raised by the parties in the notice of appeal or by a cross-appeal.”  Minn. Stat. § 176.421, subd. 6; Bradford v. Bureau of Engraving, 459 N.W.2d 697, 698, 43 W.C.D. 279, 280 (Minn. 1990).  Further, an appealing party’s brief on appeal may address only issues raised in that party’s notice of appeal.  Minn. R. 9800.0900, subp. 1.  Because issues of apportionment or credit were not at issue before the judge, and because they were neither raised nor therefore subject to being raised in the notice of appeal, issues of apportionment or credit are not properly subjects for our review and will not be addressed.

We note initially under this heading that, although they appealed from the compensation judge’s findings that the employee sustained injuries arising out of and in the course of his employment in 1978 and on December 7, 1979, from his finding that the employee is entitled to temporary total disability benefits following his several surgical procedures, and from his award of permanent partial disability benefits, the employer and insurer did not address those issues in their brief.  “Issues raised in the notice of appeal but not addressed in the brief shall be deemed waived and will not be decided by the court.”  Minn. R. 9800.0900. subp. 1.  We will therefore address ourselves only to the employer and insurer’s appeal from the judge’s award of temporary partial disability benefits.

The employer and insurer contend that the employee failed to prove (1) that his reduction in earnings was causally related to his hand and wrist condition, (2) that he conducted a diligent search for work, and (3) that his actual earnings reflected his true earning capacity.  They assert that “there is no rhyme, reason or support” for the employee’s fluctuating earnings and that the employee’s tax records are not sufficient to meet the employee’s burden of proof.  They contend that the judge’s decision “allowing benefits based on such paltry evidence” is not supported by substantial evidence.  We are not persuaded.

To demonstrate entitlement to temporary partial disability benefits, an employee must show a work-related physical disability, an ability to work subject to the disability, and an actual loss of earning capacity that is causally related to the disability.  Dorn v. A. J. Chromy Constr. Co., 310 Minn. 42, 47, 245 N.W.2d 451, 454, 29 W.C.D. 86, 91 (1976).  In Roberts v. Motor Cargo, Inc., the supreme court held that an injured employee’s actual post-injury earnings are presumed to be an accurate measure of the employee’s ability to earn.  Roberts v. Motor Cargo, Inc., 258 Minn. 425, 431, 104 N.W.2d 546, 550, 21 W.C.D. 314, 319 (1960), citing 2 Larson, Workmen’s Compensation Law § 57.21; see also Owens v. Pako Corp., 386 N.W.2d 711, 714-15, 38 W.C.D. 627, 631 (Minn. 1986).  In appropriate circumstances, however, this presumption can be rebutted.  See Einberger v. 3M Co., 41 W.C.D. 727, 739 (W.C.C.A. 1989); Borchert v. American Spirits Graphics, 582 N.W.2d 214, 215, 58 W.C.D. 316, 318 (Minn. 1998).  The presumption may be rebutted either with evidence indicating that the employee’s ability to earn is something affirmatively different from that reflected in the post-injury wage, see Einberger, 41 W.C.D. at 739, or with other evidence affirmatively establishing that the reduction in the employee’s earning capacity is unrelated to the employee’s disability, see Borchert, 582 N.W.2d at 215, 58 W.C.D. at 318.  No such evidence was offered here.

In this case, the employer’s examiner, Dr. Kern, testified that the employee was precluded from returning to his occupation as a professional football player, due in part to his diagnosed condition of Dupuytren’s contracture.  Dr. Kern also restricted the employee to light to medium work, suggesting that the employee would not be capable of heavy construction work, work assembling any large parts, or work involving repeatedly opening boxes and removing materials.  Dr. Kern’s testimony was unrefuted.

At Finding 24, the compensation judge concluded that “the employee’s job search efforts during the periods of claimed disability were reasonable, in light of all the circumstances including the lack of rehabilitation assistance provided - - with the exception of his efforts during 1990, 1991, and 1992.”  We find minimally substantial evidence to support the judge’s conclusion, principally in the credited testimony of the employee.  “Whether an injured employee makes a reasonably diligent search for suitable employment is a question of fact which must be upheld unless manifestly contrary to the evidence.”  Hanmer v. Wes Barrette Masonry, 403 N.W.2d 839, 841, 39 W.C.D. 758, 761 (Minn. 1987), citing McClish v. Pan-O-Gold Baking Co., 336 N.W.2d 538, 36 W.C.D. 133 (Minn. 1983).  Assessment of a witness’s credibility is the unique function of the trier of fact.  Brennan v. Joseph G. Brennan, M.D., 425 N.W.2d 837, 839-40, 41 W.C.D. 79, 82 (Minn. 1982), citing Spillman v. Morey Fish Co., 270 N.W.2d 781, 31 W.C.D. 187 (Minn. 1978).  Under the facts presented here, and noting the absence of any evidence offered to refute the employee’s expressly credited testimony, we cannot conclude that the judge’s award of temporary partial disability benefits was unreasonable.  See Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.

The employee argues that the compensation judge erred as a matter of law in his application of the presumption regarding earning capacity in connection with the employee’s claim for temporary partial disability benefits.  He contends that the employer failed to present any evidence, either expert or testimonial, to dispute the earning capacity of the employee as indicated by his actual earnings for 1990, 1991, and 1992.  Moreover, he argues, the judge erred also as a matter of law and fact in finding that the employee was ineligible for temporary partial disability during those years, based upon lack of a diligent job search.  We are not persuaded.

We note that in 1990 the employee’s reported taxable wages were $2,474.52.  During a significant portion of that year he also collected unemployment compensation.  The employee presented no record of earnings in 1991, and his earnings in 1992 were also minimal.  The employee offered minimal testimony regarding his efforts to find work during these three years.  While the employer and insurer presented no evidence to rebut the employee’s earning capacity, it nevertheless remains the employee’s burden to establish that his wage loss is causally related to the work injury.  Whether an injured employee’s wage loss during part-time or sporadic employment is a result of the personal injury is generally a question of fact.  In deciding this issue, the compensation judge may consider any relevant evidence on the issue, including the nature and extent of the employee’s job search.  Stauty v. Luigino’s, Inc., 52 W.C.D. 119, 124-25 (W.C.C.A. 1994).  In other words, although a diligent job search is not a prerequisite to an award of temporary partial disability benefits where an employee is released to work full-time but works only part-time, it is a factor that the judge may consider.  Kouatli v. Oildyne, slip op. (W.C.C.A. Feb. 12, 2002).  Considering the records of earnings presented by the employee and the employee’s testimony regarding the years in question, the judge could reasonably have concluded that the employee failed to prove that his wage loss was causally related to the work injury.  Accordingly, the judge’s denial of the employee’s claim for wage loss benefits in 1990, 1991, and 1992 is affirmed.  See Hengemuhle, 358 N.W.2d at 59, 37 W.C.D. at 239.