The employee appeals from the judge’s findings that his specific work injuries were temporary and that his claims for a Gillette^[1] injury were barred by notice and statute of limitation provisions. The Special Compensation Fund cross-appeals from the judge’s finding that the employee sustained a Gillette injury culminating on November 21, 1971. We affirm.

The employee played football in junior high, high school, and college. In 1959, he was a first-round draft pick by the Los Angeles Rams. He played offensive tackle for the Rams until 1960, when he was traded to the Dallas Cowboys. In 1961, he was traded to the Cleveland Browns, but, shortly thereafter, still in 1961, he was traded to the Minnesota Vikings [the employer]. At that point, he became a defensive tackle.

From 1961 to 1966, the employee played for coach Norm Van Brocklin. Coach Van Brocklin favored full contact drills and scrimmages on a daily basis. As a defensive player, the employee regularly practiced head slaps and spearing against his teammates and utilized those techniques in games. The head slaps often resulted in headaches, and the spearing often resulted in “stingers,” causing the employee to experience tingling, shooting pain, or numbness into his arms and hands. As a right defensive tackle, the employee assumed a stance that generally required him to push off with his left leg during practice and games. The employee was often hit in the back and had heavy players land on his back during both practice and games.

Throughout his years with the Vikings, the employee regularly utilized the modalities of the Vikings training room, including heat, ultrasound, and massage. Training room treatment records from July 22, 1967, through November 10, 1969,^[2] reflect that the employee made numerous visits to the training room, with comments concerning approximately 14 body parts.

On August 12, 1964, the employee sustained an injury to his cervical spine, experiencing numbness and tingling down his right arm after a head-on tackle. X-rays at the Bemidji Clinic revealed degenerative spurring of the cervical spine. The employee subsequently sustained another injury to the cervical spine on July 26, 1967, when struck on the head during practice. At that time, he laid on the ground for a short period, complaining of a pinched nerve in his neck, before getting up and resuming practice. He applied heat to his right shoulder after practice. On August 2, 1969, the employee again sustained an injury to his neck, this time during a game against Miami. The employee applied training room modalities for approximately two weeks but sought no outside medical treatment. The employer had notice of these cervical injuries.

On October 30, 1966, the employee sustained an injury to his left knee when he was struck on the lateral side of that knee during a game. The team trainer taped this knee during the remainder of the 1966 season, but the employee did not seek medical treatment. The employer also had notice of this injury.

On September 11, 1966, the employee complained of a catch in his back before the start of the game, had difficulty taking a playing stance, had difficulty standing up from that stance during the game, and had an increase in back pain during the first set of plays. He was unable to complete the game. Upon returning to the Twin Cities, he was initially seen by Dr. Donald Smiley, who reviewed x-rays, which showed no evidence of any recent bony injury. Dr. Smiley noted, “there is a little wedging of T11, both in the superior and inferior surfaces, but no evidence of any recent injury.” The employee then was hospitalized from September 13, 1966, to September 16, 1966, at Midway Hospital. X-rays taken at Midway on September 14, 1966, showed some narrowing of the disc spaces throughout the lumbar spine, particularly on the right at L3. There was also a generalized narrowing of the intervertebral disc spaces of the thoracic spine and marked spurring of the “thoracic eleven vertebral body,” which the radiologist interpreted as evidence of “a previous injury at this site.” The employee missed one game, on September 18, 1966. The employee sustained an injury to T12-L1 on September 11, 1966, and the employer had notice of that injury.

The employee continued to play football for the employer but in 1968 was replaced as the starting defensive tackle. He continued to practice but did not play as regularly thereafter.

The employee’s last day of employment with the employer was November 21, 1971, at which time he was traded to the St. Louis Cardinals, where he played five games. He continued with the Cardinals for the 1972 season as an assistant coach and then retired from football. No injuries were noted during his time with the Cardinals.

The employee first sought medical treatment for left knee symptoms on May 21, 1982, when he was examined by Dr. David Fischer. At that time, the employee was complaining that he had experienced relatively constant left knee pain, with locking over the previous six to eight months. On June 4, 1982, Dr. Fischer performed arthroscopic surgery, during which he noted the presence of a large flap tear and removed a portion of the medial meniscus. Dr. D.G. Lewallen of the Mayo Clinic performed a total left knee replacement on May 10, 2004.

The employee apparently received chiropractic adjustments to his back during his employment with the employer. The employee was seen by his primary care doctor, Dr. Wayne Thalhuber, on September 8, 1981, for diffuse pain across his back and in the left flank. Dr. Thalhuber indicated that the employee had developed pain “in July,” diagnosed chronic low back strain, and recommended exercises. A later note from sometime in 1983 indicates that the employee was taking Feldene and Tylenol #3 for low back pain. Dr. Thalhuber’s office notes of May 22, 1985, reflect that the employee was complaining of an aching in his central lumbar area that had first developed when he was playing professional football.

The employee was seen by Dr. Fischer on June 4, 1985, complaining of progressively increasing low back pain. According to the history taken at that time, the employee had had no “significant back problems during his playing years” but had experienced “intermittent trouble of a rather mild nature for a number of years, with progressively increasing discomfort” over the past two years. Dr. Fischer diagnosed severe degenerative arthrosis of the lumbosacral spine. The employee eventually underwent a lumbar laminectomy at L3-4 and L4-5 on June 30, 1992, a laminectomy at L2-3 and L3-4 on August 7, 1995, and a laminectomy at T12-L1 on June 1, 2000.

With regard to his neck, the employee was seen by Dr. David Bradford at the University of Minnesota on May 12, and July 16 and 21, 1986, for cervical spine radiculopathy. Dr. Bradford noted that x-rays showed marked spur formation and some foraminal stenosis, and he prescribed cervical home traction. When seen by neurologist Dr. John Day on April 7, 1997, the employee complained of having experienced pain in his neck that radiated into his right upper extremity over the previous five to six months. He was eventually diagnosed with cervical spondylosis with neural foraminal stenosis at C4-5-6 nerve roots. On May 26, 1999, the employee underwent right C3-4, C4-5, and C5-6 foraminotomies at Fairview-University Medical Center.

After retiring from football in 1972, the employee worked in a variety of jobs, the bulk of that work being in computer sales. He worked full time until he was almost 64 years old and then part time until he was laid off at age 70. The employee has not worked at all since approximately May of 2007.

The employee retained attorney John Horvei to represent him on October 18, 1996. At Mr. Horvei’s request, the employee was examined by Dr. Robert A. Wengler on April 29, 1998.

After also reviewing medical records, Dr. Wengler opined that the employee had severe degenerative disc disease throughout his cervical and lumbar spine, which resulted in stenosis in both the neck and the lower back at multiple levels. It was Dr. Wengler’s opinion that the employee’s “neck and back difficulties are undoubtedly secondary to multiple episodes of trauma to which he was subjected during the course of his professional football career.”

Dr. Wengler re-examined the employee on December 22, 2000. In his letter of that date, Dr. Wengler opined,

The employee filed a claim petition on December 26, 2002, claiming multiple specific injuries and a Gillette injury culminating in 1971, while the employee was in the employ of the employer. The employee was seeking temporary total, temporary partial, permanent total, and permanent partial disability benefits and medical expenses. An amended claim petition was filed on August 19, 2003, specifying twelve specific injury dates, plus the Gillette injury, and naming the appropriate workers’ compensation insurers.

The employee was examined by independent medical examiner Dr. Richard Strand on January 3, 2005, at the request of the employer and Insurance Company of North America [INA]. In a report dated May 23, 2005, Dr. Strand opined that there was no evidence that the employee’s football injuries had resulted in his subsequent severe spinal stenosis and need for multiple surgeries. It was also Dr. Strand’s opinion that the employee had not sustained a Gillette injury. Dr. Strand stated that the employee’s disability was due to “the progressive abnormalities in his spine, resulting in multiple level degenerative disc disease, and degenerative spondylosis of the cervical, thoracic, and lumbar spine.”

The employee was examined by independent medical examiner Dr. Paul T. Wicklund on January 21, 2005, at the request of the employer and Argonaut Midwest Insurance Company. In his report of February 1, 2005, Dr. Wicklund opined, in part, there was no evidence of a Gillette injury to the employee’s left knee. Similarly, Dr. Wicklund did not believe that the employee had sustained Gillette injuries to his cervical, thoracic, or lumbar spine. Dr. Wicklund also noted that the employee had congenital spinal stenosis.

On February 17, 2006, the employee was examined by Dr. Charles B. Jackson, at Mr. Horvei’s request. In a report dated October 8, 2007, Dr. Jackson diagnosed the employee with cervical spondylosis, at multiple levels, with asymmetrical multiple radiculopathies, significantly aggravated by multiple daily traumatic injuries from the employee’s football career; post-traumatic hyperextension cervical degeneration at C2-3 and C3-4, with spinal stenosis and cord compression, due to head and neck traumas that had occurred on six specific occasions listed in the doctor’s notes; post-traumatic flexion cervical degeneration at C6-7, due to head and neck trauma on those same dates; a post-traumatic compression thoracolumbar T12-L1 injury, with conus compression, due to a thoracic spine injury documented on Sept. 11, 1966, and aggravated by multiple daily traumatic insults during the employee’s football career; lumbar spondylosis with spinal stenosis at multiple levels, significantly aggravated by multiple daily traumatic insults; and post-traumatic, end-stage degenerative joint disease, left knee, as a result of multiple daily traumatic insults from football as well as specific injuries to the employee’s left knee occurring on four specific occasions, itemized in the doctor’s report, while the employee was working for the employer.

The claim petition proceeded to hearing on October 17 and 18, 2007. At that time, the employee was claiming that he had sustained ten or eleven specific injuries. In a findings and order filed on January 31, 2008, the compensation judge found that the employee had sustained specific injuries to his cervical spine on August 12, 1964, July 26, 1967, and August 2, 1969, arising out of his work activities with the employer; that the employee had sustained a work-related injury to his left knee on October 30, 1966; and that the employee had sustained an injury to the T12-L1 level of his spine on September 11, 1966. No appeal was taken from those findings. The compensation judge also found that those specific injuries were merely temporary injuries or temporary aggravations of preexisting conditions, which did not substantially contribute to the employee’s disability or need for medical treatment after 1971. The employee appeals from those findings. The judge further found that the employee had sustained a Gillette injury culminating on November 21, 1971, but that the employee did not give timely notice of that injury and that the statute of limitations had run. The employee appeals from the denial of his claims based on notice and statute of limitations. The Special Compensation Fund cross-appeals from the finding as to the occurrence of a Gillette injury.

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 (2008). 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 evidence or not reasonably supported by the evidence as a whole.” Northern States Power Co. v. Lyon Food Prods., Inc., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).

The compensation judge found that the employee sustained five specific work-related injuries. The employee appealed from the judge’s findings that the employee did not prove specific injuries to the cervical spine on September 22 or 23, 1968, or July 26, 1969, or an injury to his left knee on November 10, 1965, November 9, 1966, or August 2, 1969. However, he failed to brief those issues. Issues raised in the notice of appeal but not addressed in the appellant’s brief are deemed waived. Minn. R. 9800.0900, subp. 2.^[3] With regard to whether substantial evidence supports the judge’s findings that the specific injuries were merely temporary, we will address only those injuries found by the judge to have occurred, that is, the neck injuries of August 12, 1964, July 26, 1967, and August 2, 1969; the left knee injury of October 30, 1966; and the T12-L1 injury of September 11, 1966.

The compensation judge found that the neck injury of August 12, 1964, was a temporary aggravation of a preexisting condition. Substantial evidence supports this finding. The employee testified that he had experienced neck pain since junior high or high school. He did not recall an injury occurring specifically on August 12, 1964, and therefore could not testify as to his symptoms on that date or whether those symptoms were in any way different than those he had experienced in the past. The trainer’s injury record states only, “injury to right shoulder resulting in numbness and tingling of fingers.” There is no evidence as to whether the employee utilized modalities in the training room to treat this injury. While the x-ray taken on August 13, 1964, at Bemidji Clinic showed spurring in the cervical spine, even Dr. Jackson admitted that spurring would have preexisted this injury.^[4] The employee’s testimony and this medical evidence provide substantial evidence that the August 12, 1964, work injury was a temporary aggravation of a preexisting condition.

The compensation judge also found that the employee’s July 26, 1967, neck injury was temporary in nature. Again, the employee’s testimony supports this finding, as he did not recall this specific injury, which he categorized as a “stinger,” indicating that he had experienced stingers almost daily while playing for the employer. According to the trainer’s records, the employee was able to get back on his feet and complete practice after the injury. There was no evidence that the employee lost time from work or needed restrictions because of this injury. The trainer’s records reflect treatment that the employee received for his right shoulder that day, but there is no mention of any neck treatment on that date or any date in 1967. There is also no evidence of outside medical treatment for neck symptoms in 1967. This evidence supports the judge’s decision as to the nature of this injury.

The judge found that the employee’s August 3, 1969, neck injury was also a temporary aggravation of a preexisting condition. The employee received treatment seven times in the training room after this injury, but he received no treatment after August 16, 1969, and no outside medical treatment in the year 1969. Again, the employee could not recall this injury and therefore could not testify as to whether his symptoms were worse after this injury than they had been before. Substantial evidence supports the judge’s finding of a temporary aggravation.

In his brief on appeal, the employee questions how the judge could find these injuries to be temporary in the face of his credible testimony that he had ongoing pain over the years he played for the Vikings and after. However, the employee testified to having experienced neck pain before he played for the Vikings, and there is no evidence that these specific injuries resulted in a permanent increase in neck pain, required restrictions, required medical care, or caused the employee to miss work.^[5] Substantial evidence therefore supports the judge’s findings that these injuries were temporary.

The employee contends that Dr. Jackson and Dr. Wengler “explained the time lag from the knee injuries to the 1982 surgery by Dr. Fisher. . . . The orthopedic IMEs for the employee explained that this was the end-result of work-caused cartilaginous deterioration from the knee injuries.” The issue, however, is not whether evidence supports an alternative finding but rather whether there is substantial evidence of record to support the finding of the compensation judge.

The trainer’s injury records reflect that the employee sustained a strain of the left medial collateral ligament during a game on October 30, 1966. The knee was taped at half time of that game. The trainer’s notes reflect that the team doctor, Dr. Lannin, approved the employee to go hunting on October 31, 1966. Those same records indicate that the employee had tenderness over the left medial collateral ligament on November 1, 1966, that his left knee was injected on November 6, 1966, after which the employee played every defensive play of a game against the Packers, and that, on November 13, 1966, no injection was given, but the knee was taped for the game that day. The employee could not recall this injury and could not recall whether he had ongoing knee pain.^[7] On July 23, 1970, the employee signed a physical exam form denying any difficulty with a trick or locked knee. There is no record that the employee received any medical treatment for the left knee until 1982, when he complained of having experienced constant knee pain, with locking, for six to eight months, was diagnosed with a large flap tear of the medial meniscus, and underwent arthroscopic surgery for removal of part of the meniscus. The employee’s testimony and these records provide substantial evidence to support the judge’s finding that the 1966 left knee injury was temporary.^[8]

At the time of the employee’s injury on September 11, 1966, neither Dr. Smiley nor the radiologist at Midway noted a compression fracture at L1. Dr. Smiley diagnosed a ligamentous strain. Dr. Jackson’s opinion that the employee sustained a permanent thoracolumbar spine injury on September 11, 1966, was based on his conclusion that the employee suffered a compression fracture at L1, with associated transverse process fracture, on that date. This opinion is not supported by any medical evidence or by the opinions of Drs. Wicklund, Strand, or Wengler. While Dr. Wengler did suggest in his deposition that the employee sustained a permanent injury on September 11, 1966, there is no contemporaneous medical evidence to support such an opinion.

Given the findings on x-ray on September 12 and 13, 1966, which suggested a prior injury,^[9] the lack of evidence of a new bony injury at that time, the lack of evidence of ongoing symptomatology directly related to the September 11, 1966, injury, and the employee’s apparent ability to play the remainder of the 1966 season without medical treatment or self-treatment in the training room, substantial evidence supports the judge’s finding that the September 11, 1966, injury was temporary in nature.

The judge’s decision that the employee’s specific neck, left knee, and back injuries did not contribute to any disability or need for medical treatment after 1971 is therefore affirmed.

The compensation judge found that the employee sustained work-related Gillette injuries to his cervical spine, lumbar-thoracic spine, and left knee, culminating on his last day of employment with the employer. The judge also found that the employee has permanent impairments of his spine, his legs, his arms, and his sexual function, as a substantial result of the repetitive trauma he sustained while working as a football player for the employer. However, the judge further found that the permanency was not compensable, because the employee did not give timely notice of his Gillette injury to the employer, and because the statute of limitations had run.

Minn. Stat. § 176.141 sets forth the notice requirements for work-related injuries. Generally, the statute provides that no compensation is payable unless an employer has actual knowledge of the injury or notice of the injury is given within 180 days of the injury. The notice period does not begin to run until it becomes reasonably apparent to the employee that the injury has resulted in, or is likely to cause, a compensable disability. Metters v. Northwest Airlines, No. WC05-150 (W.C.C.A. Aug. 17, 2005), citing Issacson v. Minnetonka, Inc., 411 N.W.2d 865, 40 W.C.D. 270 (Minn. 1987). The date on which an employee has obtained sufficient knowledge to trigger the duty to give notice is a question of fact. Barcel v. Barrel Finish, 304 Minn. 536, 232 N.W.2d 13, 28 W.C.D. 4 (1975).

In the present case, the judge made no finding as to a specific date by which the employee was or should have been aware that his activities as a professional football player had contributed to a condition that was likely to become disabling and compensable. Rather, he found that

The employee testified that he had no idea that playing football was going to “create damage beyond my understanding” until “five or six or eight years later,” when a Mayo Clinic doctor told him he had the back of an old man. Medical records suggest that this conversation occurred during a August 22, 1985, visit to the Mayo Clinic. At that time, the employee gave a history of having played for the Vikings and having had recurrent episodes of neck and low back pain but continuing to play.

The employee had left knee surgery in 1982 and low back surgery in 1992. INA Exhibit 4 establishes that the employee first investigated the possibility of pursuing a workers’ compensation claim in 1985 and that he consulted attorneys in both 1985 and 1992. The exhibit goes on to reference “correspondence from this time frame” that is “included under separate cover.” That correspondence was not, however, included in the record at hearing; we know only that no legal action was taken at that time. In his brief, the employee argues that “the only permissible inference is that these attorneys did not give the Dickson a belief that they could prevail. If the opposite were true, the employee’s Claim Petition would have been filed in 1985 or 1992.” We are not persuaded. No testimony was offered as to why the employee did not file a claim petition in 1985 or 1992. A belief that he could not prevail is only one of many possible explanations. Where evidence is conflicting or more than one inference may reasonably be drawn from the evidence, the findings of the compensation judge are to be upheld. Redgate v. Sroga’s Standard Serv., 421 N.W.2d 729, 734, 40 W.C.D. 948, 957 (Minn. 1988).

The testimony of the employee and INA Exhibit 4 provide substantial evidence to support the judge’s finding that the employee was aware, prior to December of 1996, that the degenerative conditions in his knee, back, and neck were related to his work with the employer. There is no evidence that any written notice of a Gillette injury was given before the filing of the claim petition. When notice is raised as a defense to a claim, the employee has the burden to prove that notice was timely given. The employee and his wife provided no specific testimony to establish when the employee became aware that his playing days with the Vikings had led to his degenerative conditions in his neck, low back, and left knee. Given the evidence that was presented, it was not unreasonable for the judge to find that the employee knew prior to December of 1996.^[10]

The employee also argues,

The employee also argues on appeal, as he did at hearing, that

Mr. Zamberletti did testify that the employee went to the training room not only for specific injuries but also for daily aches and pains associated with practices and games. He also testified that injury and physical contacts in practice or games can lead to degenerative changes. Mr. Zamberletti did not testify that he knew that the employee had sustained a repetitive/cumulative trauma injury while working for the employer, and he deferred questions regarding medical causation to the doctors. In addition, the employee went on to play with another team after he left the employer. Perhaps most importantly, an employer cannot be deemed to have actual knowledge of an injury before the injury occurs. The employee did not appeal from the judge’s finding that the Gillette injury culminated on Nov. 21, 1971; in fact, that is the date of injury claimed by the employee. All of the employee’s visits to the Vikings’ training room occurred before that date. While it can be said that Mr. Zamberletti had knowledge that the employee was experiencing ongoing aches and pains, such knowledge does not automatically constitute knowledge of a Gillette injury.

The employee also contends that the notice statute cannot be used to bar an employee’s claims where the employer and insurer have not proven prejudice. However, prejudice is only relevant if notice is given later than thirty days but prior to 180 days after the injury. The statute makes no provision for extending the notice period beyond 180 days merely because no prejudice has been shown. See Busch v. Wal-Mart, slip op. (W.C.C.A. June 9, 2004).

Finally, the employee makes several equitable arguments as to why his claims should be found compensable. The wisdom of the 180-day notice period, however, is a matter for the legislature, not this court. It is also not our function to substitute our judgment for that of the compensation judge on a factual issue. The judge’s decision denying benefits based on the employee’s failure to provide timely notice of his Gillette injury is therefore affirmed.

The employee contends that the statute of limitations was satisfied by the employer’s provision of a training room where the employee self-treated and was taped by the trainer. However, because we have affirmed the judge’s finding that the employee did not give timely notice of his Gillette injury, we need not consider the question of whether the employee’s claim is barred based on the running of the limitations period. Lack of requisite notice, alone, is fatal to the employee’s claims.

Because we have affirmed the judge’s decision denying the employee compensation, we need not address the Special Compensation Fund’s cross-appeal concerning the judge’s Gillette injury finding.