Leigh Corporation and ACE USA/ESIS, Inc. appeal from the compensation judge’s finding that the employee sustained a work-related injury to his right knee on July 22, 1982, and from the judge’s finding apportioning liability between the employee’s 1982 and 1995 injuries. We affirm.

On July 22, 1982, Brian Harding [the employee] was working for Leigh Corporation [Leigh] when he fell ten to fifteen feet from a ladder onto the pavement below. He was transported by ambulance to North Memorial Medical Center, where he was treated primarily for complaints of low back and right hip pain. X-rays obtained of the employee’s lumbosacral spine, pelvis and right hip, and skull were all reported as negative. The emergency room physician diagnosed a back strain and concussion and released the employee to be followed by his family physician.

The employee was seen at the Elk River Clinic by Dr. R. K. Sommer on July 26, 1982.^[1] On that visit, the employee complained of back pain in his lower thoracic spine. Dr. Sommer obtained x-rays of the thoracic spine, which he interpreted as showing a collapsed disc space at the T11-T12 level. He diagnosed a compression fracture or a collapse of the “cartilaginous portion between the discs.”

Leigh and its workers’ compensation insurer, ACE USA/ESIS, Inc. [ACE] accepted liability for the employee’s injury and commenced payment of wage loss benefits. On November 3, 1982, the employee was examined at the request of Leigh and ACE by orthopedist Dr. Ivan Schloff. Dr. Schloff obtained a history from the employee, performed an examination, and obtained x-rays. He diagnosed a “history of lumbosacral strain” and recommended that the employee undergo a CT scan to rule out a possible herniated L4 disc, concluding that the employee was capable of working at a job not requiring repeated bending or lifting of over twenty-five pounds. The scan was performed on November 15, 1982, and was read to reveal some decrease in the T11-T12 disc space and degenerative disc disease at that level, but no evidence of a herniated disc. On November 29, 1982, ACE, which had paid wage loss benefits to the employee from July 23, 1982, through November 19, 1982, filed a Notice of Intention to Discontinue the employee’s temporary total disability benefits.

On December 3, 1982, the employee was examined by orthopedist Dr. Francis Trost. Dr. Trost diagnosed post-traumatic right low back pain related to the employee’s fall on July 22, 1982. He noted that the “[employee] tends to stand on his left leg with his right leg flexed and this may be due to the damage to his upper gluteal muscles which are painful when put under stretch by fully extending the leg or weighing [sic] it.” Dr. Trost recommended a back support, physical therapy, and non-steroidal anti-inflammatory medication.

The employee filed an Objection to Discontinuance on December 30, 1982, and the matter was heard by a compensation judge on May 20, 1983. The issue presented to the judge was whether the employee was either temporarily totally disabled or temporarily partially disabled from November 20, 1982, to the date of hearing, as a result of his July 22, 1982, work injury. Evidence submitted at that hearing included the deposition testimony of Drs. Sommer, Trost, and Schloff.^[2] In a Findings and Order issued August 24, 1983, the judge found the employee’s diagnosis to be lumbosacral strain and concluded that the employee could work within his physical limitations. The judge further determined that the employee had withdrawn himself from the labor market, and she denied the employee’s claim for wage loss benefits. No claim had been made at that time that the employee’s July 22, 1982, work injury included an injury to his right knee.

The employee evidently continued to see Dr. Sommer after the May 20, 1983, hearing, and he was eventually referred by Dr. Sommer to orthopedic surgeon Dr. Philip Haley for evaluation of right knee complaints. In a history provided to Dr. Haley on August 29, 1983, the employee described pain in the medial aspect of his right knee that he had noticed “as of the spring of this year.” The employee reported that he was not aware of any specific injury, but he did advise the doctor of his injury on July 22, 1982. Dr. Haley diagnosed possible medial meniscus lesion, and he recommended arthroscopic surgery.

The employee was seen for a pre-op physical by Dr. Sommer on August 31, 1983. In the history portion of his report, Dr. Sommer noted that he had seen the employee on June 10, 1983, “with a history of increasing soreness of the right knee for the previous 3-4 weeks.” The doctor noted also that the employee’s symptoms correlated well “with increasing activity and work load for the past 6 weeks with his new business.” He noted also that “[the employee] ha[d] been recovering from a prolonged symptomatic back contusion - compression fracture ligament[ous] sprain with right lower extremity radiculitis. This accident was suffered 7-22-82.” Dr. Sommer cleared the employee for surgery, and Dr. Haley performed an arthroscopic right medial meniscectomy the following day.

In a letter addressed to Illinois Mutual Life and Casualty Company [Illinois Mutual] on November 1, 1983, Dr. Sommer discussed the employee’s right knee condition and its relationship to the 1982 work injury.^[3] He stated that the injury had led to severe back discomfort, with right lower extremity weakness and lumbar radiculitis. He noted that the employee, secondary to radicular discomfort, walked with continued flexion of his right knee and with splinting of the entire right lower extremity. Dr. Sommer went on to state that by the early spring of 1983, with improved back function and greater use of his right leg, the employee had become increasingly symptomatic in his right knee. He concluded his letter by stating:

Dr. Haley also addressed causation of the employee’s right knee condition in a letter to Illinois Mutual on November 23, 1983. He reported that the employee had sustained an injury to his right knee while at work on July 22, 1982, explaining that the employee’s torn medial meniscus was a traumatic condition and not a disease process aggravated by ordinary activity. On November 30, 1983, he issued a follow-up letter, after reviewing additional medical records submitted to him by Illinois Mutual. In that letter, he acknowledged that the additional records did not specifically mention the knee, but he went on to explain that the employee continued to relate the onset of his knee problems to the 1982 work injury. He noted also Dr. Sommer’s letter of November 1, 1983, and he concluded his letter as follows:

The employee had a good result from the 1983 arthroscopic surgery, and he was able to return to full-time employment without restrictions attributable to his right knee condition. In August of 1988, he was hired by Central Lutheran Church [Central Lutheran] to work as a custodian. On June 15, 1995, the employee injured his right knee and right shoulder when he slipped and fell at Central Lutheran. He subsequently sought treatment for his knee and shoulder on January 15, 1996, with orthopedist Dr. Randall Norgard. Dr. Norgard assessed right knee pain with probable medial meniscal tear and an anterior glenoid labral tear in the right shoulder. The employee underwent a right knee arthroscopy with partial medial meniscectomy on February 23, 1996, and an arthroscopic procedure on the right shoulder on May 3, 1996, both performed by Dr. Norgard.

By December 9, 1996, Dr. Norgard reported that the employee had reached maximum medical improvement in regard to his right knee and right shoulder conditions. In a Health Care Provider Report issued ten days later, Dr. Norgard rated the permanent partial disability of the employee’s knee at 2% of the whole body under Minnesota Rules 5223.0510, subpart 3B(1). Central Lutheran and its insurer, State Farm Insurance Company [State Farm], accepted liability for the employee’s 1995 injury and paid wage loss, permanency, and medical benefits.

The employee returned to see Dr. Norgard with complaints of right knee pain on November 11, 1999. At that visit, the doctor noted that the employee had undergone an arthroscopic exam of his left knee on July 2, 1999, and carried a diagnosis of degenerative joint disease in that knee. Dr. Norgard assessed degenerative joint disease in the right knee as well, recommended that the employee avoid kneeling, and treated him with anti-inflammatory medication.

In a letter addressed to State Farm on March 18, 2005, Dr. Norgard discussed the employee’s right knee injuries. He opined that both the 1982 and 1995 right knee injuries were substantial contributing factors in the employee’s need for the surgery performed on February 23, 1996. He further opined that the employee’s progressive right knee degenerative joint disease was the result of both the 1982 injury and the 1995 injury, and he noted that, at the time of the employee’s 1996 surgery, significant degenerative arthritis was already present.

By June 20, 2005, conservative treatment was no longer effective, and Dr. Norgard recommended that the employee undergo a total right knee arthroplasty. This surgery was performed on August 31, 2005, and was followed three months later by the need to manipulate the knee under anesthesia.

On January 11, 2006, the employee was examined by orthopedic surgeon Dr. Joel Boyd at the request of State Farm. Dr. Boyd obtained a history from the employee, reviewed medical records, and performed a physical examination. In a report dated January 19, 2006, Dr. Boyd offered the opinion that the employee had sustained a right knee injury in 1982 resulting in a meniscal tear and subsequent surgery. He acknowledged that, while it was difficult to state exactly when the tear had occurred, “[g]iven the circumstances that [the employee] was not ambulating with a normal gait following the 1982 injury, . . . [e]ither directly or indirectly, the meniscus tear and surgery in 1983 would be related to the 1982 injury.” Dr. Boyd opined that the employee had sustained another medial meniscus tear in 1995, and that the first meniscus tear had not caused the second tear. He apportioned 90% of the employee’s medical treatment and wage loss in 1995 and 1996 to the 1995 injury and 10% to the 1982 injury. He then opined that the employee had sustained a third, Gillette-type,^[4] injury to the right knee culminating on or about June 19, 2005, apportioning 15% liability for the current right knee condition to the 2005 Gillette injury, 35% to the 1995 injury, and 50% to the 1982 injury.

Leigh and ACE arranged for a medical evaluation by orthopedist Dr. Michael D’Amato on January 30, 2006. In a report dated February 6, 2006, Dr. D’Amato related the history he obtained from the employee, the specific medical records he reviewed, and his findings on examination. With respect to the cause of the employee’s initial medial meniscal tear, Dr. Amato opined that there was no evidence from the employee’s July 22, 1982, injury that would correspond with an injury to his medial meniscus. He opined that the cause of the employee’s meniscal tear, first documented by Dr. Haley in August 1983, was indeterminate. Dr. D’Amato opined further that the employee’s 1995 injury played a factor in increasing the development of the employee’s degenerative joint disease but that, because the employee’s osteoarthritis was already in existence, that injury played only a partial role in the employee’s subsequent need for an arthroplasty procedure. As to the issue of apportionment, Dr. D’Amato attributed 75% of the employee’s ongoing right knee condition to his indeterminate condition in 1983 and 25% to his 1995 injury and 1996 surgery.

On August 1, 2005, the employee had filed the first in a series of claim petitions seeking wage loss and medical benefits continuing from June 20, 2005. Central Lutheran and State Farm ultimately agreed to pay benefits to the employee pursuant to a Temporary Order and subsequently filed a Petition for Contribution and/or Reimbursement against Leigh and ACE. The various pleadings were consolidated by an Order served and filed April 7, 2006, and the matter eventually came on for a hearing before a compensation judge on May 22, 2007.

Just prior to trial, in a letter to the employee’s attorney dated May 9, 2007, Dr. Norgard offered additional opinions regarding the employee’s injuries. He noted that, in addition to having reviewed his own medical chart, he had also reviewed records of Dr. Philip Haley and reports of the IMEs conducted by Drs. Boyd and D’Amato. He again concluded that the 1982 and 1995 injuries were both substantial contributing factors to the employee’s disability and need for medical treatment. Dr. Norgard noted that, at the time of the employee’s second right knee arthroscopic surgery, he had found Grade II and Grade III chondromalacia changes in the right medial femoral condyle in the weight bearing position, degenerative changes in the medial tibial plateau, and a large degenerative tear in the posterior horn of the medial meniscus. Dr. Norgard apportioned 65% of liability for the employee’s “current knee condition” to the July 22, 1982, injury and 35% to the June 15, 1995, injury.

The employee withdrew his claims relative to his left knee injuries, and the only issues remaining were whether the employee had sustained a right knee injury on July 22, 1982, and, if so, whether State Farm was entitled to contribution from ACE. The employee testified at trial that he had injured his right knee when he fell from the ladder in 1982. He explained that immediately after the injury it was his low back that hurt the most but that he also had pain down his right leg that went through his knee. He testified that, once his low back and right leg pain improved, his right knee symptoms worsened.

In a Findings and Order issued July 23, 2007, the compensation judge found that the employee sustained an injury to his right knee at Leigh on July 22, 1982. She found also that the 1982 and 1995 right knee injuries were both substantial contributing factors in the employee’s wage loss and his need for medical treatment and rehabilitation services. With respect to the employee’s disability and need for treatment in 1995 and 1996, the judge accepted Dr. Boyd’s apportionment opinion assessing 10% responsibility to the 1982 injury and 90% to the 1995 injury. She found Dr. Boyd’s opinion to be “credible [and] consistent with the evidence of the case.” With respect to liability for benefits paid following the employee’s right knee arthroplasty in 2005, the judge accepted Dr. Norgard’s opinion apportioning 65% to the 1982 injury and 35% to the 1995 injury, and she ordered reimbursement accordingly. Leigh and ACE appeal.

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 (2006). 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., 304 Minn. 196, 201, 229 N.W.2d 521, 524 (1975).

The first issue on appeal is whether the judge’s finding that the employee sustained an injury to his right knee on July 22, 1982, is supported by substantial evidence in view of the entire record as submitted. Leigh and ACE contend that neither the contemporaneous medical records nor the ensuing litigation and medical depositions that were a part of that litigation in 1983 support the judge’s determination. Not until Dr. Haley’s examination on August 29, 1983, they contend, is there a medical record that references pain in the medial aspect of the employee’s right knee. And even on that occasion, they argue, Dr. Haley reported that the employee first noticed the pain as of the spring of 1983 and was unaware of any specific injury. They contend further that the rationale expressed for the judge’s decision is based on a misinterpretation and misstatement of the employee’s medical records. They argue finally that Dr. D’Amato was the only doctor who outlined the evidence he reviewed in preparing his report and that it appears also that he was the only doctor provided with the information necessary for a properly founded opinion. We are not persuaded.

In her memorandum, the judge noted that, although the employee’s back injury was the focus of his complaints and medical care after his fall from the ladder, she was not convinced by Dr. D’Amato’s opinion that there was no evidence to correlate the employee’s knee symptomatology with the fall. While the judge did not expressly adopt the causation opinion set forth in Dr. Sommer’s letter of November 1, 1983, the judge’s explanation does parallel Dr. Sommer’s opinion. Dr. Sommer specifically found the employee’s knee problem to be “a complication and concomitant result of that fall suffered July 22, 1982.” Dr. Sommer was the employee’s treating physician in 1982 and 1983, and, having examined the employee on at least twenty occasions prior to authoring that letter, had personal knowledge of the employee’s complaints, findings, and diagnoses. Dr. D’Amato made no reference to Dr. Sommer’s causation opinion in his report of February 6, 2006.

It appears that the judge also relied on the causation opinions of Dr. Haley. In his letter of November 23, 1983, Dr. Haley specifically stated that the employee sustained an injury to his right knee on July 22, 1982. And, on November 30, 1983, after reviewing additional medical records, including Dr. Sommer’s November 1, 1983 report, he again stated that the need for the employee’s right knee surgery was “directly related” to the 1982 work injury.

While another factfinder may have viewed the evidence in this case quite differently, we cannot conclude that the judge erred in implicitly accepting the opinions of Drs. Sommer and Haley. Resolution of conflicting medical expert opinion is the responsibility of the compensation judge, and the trier of fact’s choice between medical experts must be upheld so long as there is adequate factual foundation for the opinion accepted by the judge. See Nord v. City of Cook, 360 N.W.2d 337, 37 W.C.D. 364 (Minn. 1985). It is clear from her memorandum that the judge reviewed and weighed the medical opinions in the context of the employee’s limited recollection of his 1982 injury and the medical records and that she found the opinions of the treating doctors more persuasive than those of Dr. D’Amato. The evidence as a whole adequately supports the opinions of Drs. Sommer and Haley, and the compensation judge did not err in relying on those opinions in concluding that the employee sustained a right knee injury on July 22, 1982. We must, therefore, affirm.

The compensation judge apportioned liability for the employee’s total right knee replacement by attributing 35% responsibility to the June 15, 1995, injury and 65% to the July 22, 1982, injury. In arriving at this determination, the judge adopted the opinion of the employee’s treating surgeon, Dr. Norgard. Leigh and ACE contend that the judge erred in adopting Dr. Norgard’s opinion because it lacked adequate foundation. They argue that the judge’s statement that Dr. Norgard “was familiar with both of the employee’s injuries and his treatment and disability” lacks support in the record. They contend that Dr. Norgard was not a treating physician or surgeon in 1982 or 1983 and that there is no indication in any record submitted into evidence that Dr. Norgard ever reviewed the records of Dr. Sommer, Dr. Trost or Dr. Schloff or those from North Memorial. Further, they note that Dr. Norgard acknowledged that he was not aware of the mechanism or nature of the 1982 injury, nor did he provide any causation opinion regarding that injury. We are not persuaded.

Foundation goes to the competence of a witness to provide an expert opinion, which depends both upon the witness’s scientific knowledge and his or her practical experience with the subject matter at issue. Drews v. Kohl’s, 55 W.C.D. 33, 39 (W.C.C.A. 1996), citing Reinhardt v. Colton, 337 N.W.2d 88, 93 (Minn. 1983). In the present case, Dr. Norgard obtained a history from the employee, personally examined him on a number of occasions, and provided treatment to him for his right knee condition. He performed the employee’s arthroscopic surgery in 1996 and his right knee arthroplasty in 2005. In addition to his own extensive medical chart, Dr. Norgard also reviewed Dr. Haley’s records and the detailed narrative reports prepared by Dr. Boyd and Dr. D’Amato. The fact that Dr. Norgard was not the treating surgeon in 1983, was not aware of the mechanism of the 1982 injury, and may not have reviewed the records contemporaneous with the employee’s fall from the ladder may go to the persuasiveness or weight afforded his opinion by the judge, but it does not render the opinion without foundation. See, e.g., Goss v. Ford Motor Co., 55 W.C.D. 316 (W.C.C.A. 1996); Simons v. Ridgeview Med. Ctr., No. WC06-211 (W.C.C.A. Dec. 1, 2006). We accordingly conclude that there was adequate foundation for Dr. Norgard’s opinion.

Leigh and ACE argue also that the judge committed an error of law by failing to consider factors articulated in precedent case law for equitable apportionment of liability. Factors to be considered in equitable apportionment, they argue, include the nature and severity of the injuries at issue, the employee’s symptoms following each injury, and the period of time between the injuries. See Goetz v. Bulk Commodity Carriers, 226 N.W.2d 888, 27 W.C.D. 797 (Minn. 1975). Had the judge applied these principles and factors to the facts presented in the instant case, they contend, she would not have found the 1982 injury 65% responsible for the employee’s current right knee condition. We are not persuaded.

We note first that an “apportionment decision can, of necessity, be based on no predetermined and precise formulas, but must be determined based upon the facts of each case.” Goetz, 226 N.W.2d at 891, 27 W.C.D. at 800. Moreover, as a finding of equitable apportionment is factual in nature, the judge’s determination should be affirmed where it is supported by substantial evidence in view of the entire record as submitted. Sundquist v. Kaiser Eng’rs, Inc., 456 N.W.2d 86, 88, 42 W.C.D. 1101, 1103 (Minn. 1990); DeNardo v. Divine Redeemer Mem. Hosp., 450 N.W.2d 290, 293, 42 W.C.D. 626, 629 (Minn. 1990). In reviewing her detailed memorandum, we see no indication that the judge was unmindful of the nature of the employee’s first surgery, his symptoms and restrictions following that injury, or the fact that the employee had little problem with his right knee until 1995.

We note also that, while they do not agree on the apportionment, all three doctors who have offered apportionment opinions do agree that the 1982 injury plays a more significant role in the employee’s condition than does the 1995 injury. In apportioning 65% of the employee’s disability to the 1982 injury, Dr. Norgard reported that, at the time of the employee’s right knee arthroscopic surgery on February 23, 1996, there were Grade II and Grade III chondromalacia changes in the weight bearing portion of the right medial femoral condyle. There was also degenerative change in the medial tibial plateau and a large degenerative tear in the posterior horn of the medial meniscus. As it was based on adequate foundation, the judge was entitled to accept Dr. Norgard’s opinion. We will not substitute our judgment for that of the compensation judge. We therefore affirm the judge’s apportionment determination.