The employee appeals from the compensation judge’s decision as to the extent of his permanent partial disability.  We affirm.

On December 24, 1983, the employee sustained a right knee injury in the course and scope of his employment with Jacobson Transport [the employer].  Several arthroscopic procedures were performed to treat this injury over the years and, eventually, in July 2007, the employee underwent a total right knee arthroplasty.

The employer and insurer paid the employee benefits for a 37% permanent partial disability of the leg.  The employee claimed entitlement to benefits for a 50% permanent partial disability, or an additional 13%, and the matter came on for hearing before a compensation judge on June 3, 2009.^[2]

Relevant evidence included permanent partial disability opinions by Dr. Michael Holte, one of the employee’s treating physicians, and Dr. Nolan Segal, the employer and insurer’s independent examiner.  In a decision issued on August 21, 2009, the compensation judge concluded that the employee had a “presently ascertainable” 37% permanent partial disability.  The employee 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 (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).

In a report dated December 14, 2007, Dr. Holte concluded that the employee had a 50% impairment of the lower extremity, based on having undergone a total knee arthroplasty with a fair result.  Noting that the employee’s injury occurred prior to January 1, 1984, Dr. Holte indicated that he had based his permanency rating on the fourth edition of the AMA Guides to Evaluation of Permanent Impairment.  Dr. Segal, in contrast, consulted the fourth, fifth, and sixth editions of the AMA Guides, concluding, following his April 9, 2008, evaluation, that the employee was subject to a 37% impairment as a result of his work-related right knee condition.  In her finding on the issue, the compensation judge determined as follows:

An employee’s right to benefits is generally governed by the law in effect on the date of the employee’s injury.  See, e.g., Joyce v. Lewis Bolt & Nut Co., 412 N.W.2d 304, 40 W.C.D. 209 (Minn. 1987).  The problem with the employee’s argument here, however, is that nothing in the law in effect on the date of the employee’s injury^[3] required the use of any particular system to rate an employee’s permanent impairment.^[4]  For pre-1984 or so-called “old law” injuries, “the statute does not prescribe a rule or method of determining the extent of disability.”  Hosking v. Metropolitan House Movers Corp., 272 Minn. 390, 397, 138 N.W.2d 404, 409, 123 W.C.D. 673, 685 (1965), quoting Gurtin v. Overland-Knight Co., 179 Minn. 38, 39, 228 N.W. 169, 169 (1929).  Instead, “[i]t is left to the judgment of the trier of fact.” Id; see also Erickson by Erickson v. Gopher Masonry, Inc., 329 N.W.2d 40, 43, 35 W.C.D. 523, 528 (Minn. 1983); Jacobowitch v. Bell & Howell, 404 N.W.2d 270, 274, 39 W.C.D. 771, 778 (Minn. 1987) (a finding as to permanent partial disability is one of ultimate fact).

The compensation judge accepted the opinion of Dr. Segal, as opposed to Dr. Holte, because the employee had gained additional function following Dr. Holte’s examination.  While the judge was not required to base her decision on expert opinion, see Hosking, 272 Minn. at 397, 138 N.W.2d at 409, 123 Minn. at 685, she was entitled to do so.  Because the judge’s decision on permanent partial disability was reasonable and supported by the record as a whole, and because we reject the employee’s argument regarding the applicable AMA Guides, we affirm the judge’s 37% permanent partial disability rating.