¶ 45. (dissenting). The LIRC concluded that two surgical procedures necessary to repair one anterior cruciate ligament injury result in a 20 percent permanent partial disability of Glenn R. May's left leg at the knee. The majority opinion concludes this is reasonable, even though the only medical evidence admitted places May's disability at 10 percent. Majority op., ¶ 2. It does so largely because of the deference it accords the LIRC's interpretation of Wis. Stat. § 102.18(1)(d) and Wis. Admin. Code § DWD 80.32(4). Id. The standards of review the majority opinion employs prevent a reasoned analysis of the legal issue presented, which when undertaken, demonstrates that May incurred one scheduled permanent disability, the extent of which is a factual determination that turns on the functional condition of his knee after he reached his final healing *33plateau. Because proof of the existence and the extent of a functional disability are factual issues to be determined when a scheduled permanent disability is under consideration and because the LIRC's factual determination is contrary to uncontradicted, credible medical evidence that the extent of May's scheduled permanent disability is 10 percent, the LIRC's decision is not supported by credible and substantial evidence and therefore is erroneous. Accordingly, I respectfully dissent.
I. BACKGROUND
¶ 46. The dispositive facts are not disputed. In 1999, May suffered a workplace injury to his left knee. As a result of that injury, he had two surgical procedures performed on May 5,1999: a meniscectomy and an anterior cruciate ligament autograft.1 Daimler-Chrysler paid May temporary total disability during his recuperative period. When May returned to work and had reached a healing plateau, the orthopedic surgeon who performed the knee surgery, Dr. Ansari, opined that the injury caused May a 15 percent permanent partial disability of his left leg at the knee, due to a 5 percent disability caused by the torn meniscus and a 10 percent disability caused by the torn anterior cruciate ligament.
¶ 47. After several months at work, May's knee began to interfere with his work, in that it swelled, was painful and was stiff. He again consulted Dr. Ansari, who opined that the first anterior cruciate repair had not held up well. He recommended a second surgery. The second surgery did not involve a meniscectomy, but involved a repair of only the anterior cruciate ligament, *34this time with an allograft.2 Following the second surgery, May again was paid temporary total disability until he returned to work. Once he had reached a healing plateau, Dr. Ansari opined that the second surgery had been successful in repairing May's torn anterior cruciate ligament and that May's permanent partial disability had not increased beyond the 10 percent level he had prior to the second surgery. Dr. Ansari explained, "He has 10 percent PPD to the left knee due to ACL reconstruction. In my opinion his PPD has not changed due to redo of his anterior cruciate ligament." (Emphasis added.)
¶ 48. The LIRC rejected Dr. Ansari's medical opinion that the permanent condition of May's knee had not changed subsequent to the second surgery, and instead it adopted the opinion of an administrative law judge who stacked two minimum disability percentages for anterior cruciate ligament repair found in Wis. Admin. Code § DWD 80.32(4). The majority opinion affirms the LIRC's determination that stacking minimum disability values from § DWD 80.32(4) is reasonable even though the benefits awarded are more than 5 percent higher than the uncontradicted, credible medical evidence in the record. Majority op., ¶ 3.
II. DISCUSSION
A. Standard of Review
¶ 49. We review the LIRC's decision, not that of the circuit court. Stafford Trucking, Inc. v. DILHR, 102 Wis. 2d 256, 260, 306 N.W.2d 79 (Ct. App. 1981). The cause and the extent of a disability under worker's *35compensation law are questions of fact for which the LIRC's determination is conclusive if supported by credible and substantial evidence. Wis. Stat. § 102.23(6);3 Vande Zande v. DILHR, 70 Wis. 2d 1086, 1095, 236 N.W.2d 255 (1975) (citing Transamerica Ins. Co. v. DILHR, 54 Wis. 2d 272, 276, 195 N.W.2d 656 (1972)). When "facts are undisputed and only one reasonable inference can be drawn from the facts and that inference is contrary to the conclusion drawn by LIRC, we must overrule LIRC." Leist v. LIRC, 183 Wis. 2d 450, 458, 515 N.W.2d 268 (1994). The application of statutes or administrative rules are questions of law. Beecher v. LIRC, 2004 WI 88, ¶ 22, 273 Wis. 2d 136, 682 N.W.2d 29. Although the majority opinion correctly sets out the standards of review that are often employed when we review an agency's application of statutes or administrative rules, majority op., ¶ 2, this case turns on whether the LIRC can ignore uncontradicted, credible medical evidence and substitute its own judgment about the existence and the extent of a medical condition.
B. Permanent Partial Disability
1. General principles
¶ 50. A worker who has suffered a work-related injury may recover for a permanent disability at the end *36of his healing period. Wis. Stat. § 102.44(2)-(4). There are two categories of permanent disability: permanent total disability and permanent partial disability. See § 102.44(2) and (4). Each type of permanent disability resulting from a work-related injury is further separated into two types of disabilities: scheduled disabilities and unscheduled disabilities. Langhus v. LIRC, 206 Wis. 2d 494, 498-99, 557 N.W.2d 450 (Ct. App. 1996).
¶ 51. The scheduled disabilities are addressed in Wis. Stat. §§ 102.52, 102.53 and 102.55. Id. at 498. The total benefits for an injury that results in a scheduled permanent disability to a body part are established by the benefit weeks set out in § 102.52(1)-(18). Id. at 498-99. If the type of permanent disability listed in the statute results in less than a total permanent disability of the body, the benefit weeks are calculated as a percentage of loss of function for that part of the body that is listed in the schedule. Wis. Stat. § 102.55(3). With a scheduled disability, the benefits are limited, as directed by Wis. Stat. § 102.44(4).4 Hagen v. LIRC, 210 Wis. 2d 12, 23, 563 N.W.2d 454 (1997); Langhus, 206 Wis. 2d at 498.
¶ 52. If the work-related permanent disability is not a disability that is scheduled under Wis. Stat. §§ 102.52, 102.53 or 102.55, it is characterized as an "unscheduled" permanent disability. Hagen, 210 Wis. 2d at 18. When the permanent disability is unscheduled, a loss of earning capacity is not presumed to follow a loss *37of function. Kurschner v. DILHR, 40 Wis. 2d 10, 18, 161 N.W.2d 213 (1968). Rather, a loss of earning capacity in the same or other suitable employments is a crucial element that the injured employee must prove before an unscheduled permanent disability can be found to exist. N. States Power Co. v. Indus. Comm'n, 252 Wis. 70, 73-74, 30 N.W.2d 217 (1947).
¶ 53. If the injury causes an unscheduled permanent disability that is partial, the benefits are calculated by determining the percentage of disability as "compared medically with injuries that would render a person permanently totally disabled for industrial purposes as provided in sec. 102.44(2) . . . ."5 Kurschner, 40 Wis. 2d at 18. The calculation of benefits due to an unscheduled disability is accomplished by applying the percentage of loss of earning capacity to 1,000 benefit weeks. Wis. Stat. § 102.44(3). A back injury is an unscheduled injury. Hagen, 210 Wis. 2d at 23; Pfister & Vogel Tanning Co. v. DILHR, 86 Wis. 2d 522, 523, 273 N.W.2d 293 (1979); Langhus, 206 Wis. 2d at 501.
¶ 54. An accurate analysis of the proof that is sufficient to support a worker's compensation award for a permanent disability requires an initial classification of whether the disability is scheduled or unscheduled. See Pfister, 86 Wis. 2d at 527-28. This is so because an unscheduled permanent disability benefit cannot be based solely on an impairment of bodily function, but also requires proof of an impairment of earning capacity. Id. However, proof of a scheduled disability will be sufficient if that proof establishes a functional medical impairment to a body part. Id.; Mednicoff v. DILHR, 54 *38Wis. 2d 7, 12, 194 N.W.2d 670 (1972). In explaining the different analyses to be applied to an unscheduled disability as compared with a scheduled disability, we noted that,
[I]t appears that the injuries of an applicant (non-schedule but permanent total or partial) are to be compared medically with injuries that would render a person permanently totally disabled for industrial purposes as provided in sec. 102.44(2), Stats., and not to injuries that would totally disable a person functionally without regard to loss of earning capacity.
Id. at 11 (citing Kurschner, 40 Wis. 2d at 18).
¶ 55. Most of the disabilities listed in Wis. Admin. Code § DWD 80.32 are scheduled disabilities. However, a permanent disability of the back, § DWD 80.32(11), is an unscheduled disability. Hagen, 210 Wis. 2d at 23; Langhus, 206 Wis. 2d at 501; see also Pfister, 86 Wis. 2d at 523. We have held that the LIRC errs when it determines the extent of an unscheduled permanent disability by comparing the "employee's injuries to those of a hypothetical person totally disabled functionally and not to one totally disabled as to loss of earning capacity." Pfister, 86 Wis. 2d at 529. And as explained above, proof of loss of earning capacity is not required of a scheduled permanent disability because unscheduled and scheduled permanent disabilities have different foundations. Kurschner, 40 Wis. 2d at 18. The proof of a scheduled permanent disability is complete once the functional level of the disability has been proven, regardless of its actual impact on the employee's earning capacity. Mednicoff, 54 Wis. 2d at 12. Stated otherwise, the legislature has presumed a loss of earning capacity as a part of the number of benefit weeks it chose for each category of scheduled permanent disability. Id. The LIRC cannot change the permanency schedules *39established in the statutes or the proof required to accord benefits under those schedules. Leist, 183 Wis. 2d at 457; Wis. Stat. § 102.55(3); Wis. Stat. § 102.44(4).
2. May's permanent disability
¶ 56. May's work-related injury to his knee caused a scheduled permanent disability.6 Wis. Stat. § 102.52(11); Mednicoff, 54 Wis. 2d at 13; Langhus, 206 Wis. 2d at 501. Accordingly, May's compensation for the permanent partial disability to his leg at the knee is limited by statute. Hagen, 210 Wis. 2d at 23.
¶ 57. The LIRC cannot base its judgment about the existence and the extent of May's disability on speculation. Leist, 183 Wis. 2d at 457. To do so would permit the LIRC to exercise its judgment arbitrarily. Id. The statutory provisions are May's exclusive remedy. Id. In order to qualify as a permanent disability, a knee injury requires medical proof of the existence and functional extent of the change in condition of the knee. Wis. Stat. §§ 102.13(1)7 and 102.52(11).
*40¶ 58. Here, the report of Dr. Ansari was received into evidence without objection. Therefore, it is prima facie evidence of the existence and the extent of May's permanent partial disability. Leist, 183 Wis. 2d at 459. Dr. Ansari gave the only contemporaneous opinion of the actual condition of May's knee. He was May's treating physician for many years. He had repeatedly seen May and evaluated his medical condition and May's resulting permanent disability. The minimum percentage of disability set out in Wis. Admin. Code § DWD 80.32(4), i.e., 10 percent permanent partial disability for an anterior cruciate ligament repair, is only an average value based on a state-wide survey of physicians. It is not patient-specific, and therefore, it is not competent evidence of the actual condition of May's knee. Absent some reason to reject Dr. Ansari's opinion, the percentages of permanency set out in § DWD 80.32(4) cannot contradict Dr. Ansari's particularized medical evaluation of May's actual disability. Let me explain.
¶ 59. The Worker's Compensation Advisory Council (Advisory Council) assisted in establising Wis. Admin. Code § DWD 80.32 as guidelines that physicians were to consult in determining the levels of permanent disability for individual claimants. The guidelines were constructed after consultation with physicians throughout the state, who responded to the survey based on their experiences with many patients. A large revision to these guidelines was made in 1973-74 and again in 1993-94 to form the current version of § DWD 80.32.
*41¶ 60. The physician surveys used for these updates asked physicians to comment about the effect on the condition of various parts of the body for a variety of injuries and repairs. The results from the 1993 survey were tabulated by four administrative law judges and a worker's compensation assistant, Margaret O'Connell. They chose the values for some subsections of § DWD 80.32 due to the "substantial agreement among the doctors" and in other areas where there was "such substantial disagreement" they made no recommendation. Margaret O'Connell March 16,1993 Memorandum to Worker's Compensation Advisory Council Sub-Committee Members (hereinafter "O'Connell Memorandum"). In regard to permanent disability of the leg at the knee, O'Connell related:
B1 & 2. We believe 102.32(4) should be amended to show that the 5 percent minimum for removal of semi-lunar cartilage applies to all procedures open or closed, total or partial since there has been an interference with the anatomical structure of the knee. The Department has attempted to interpret the current rule in this manner but with disputes from carriers and increases in litigation which would be avoided with amendment.
B3. We would give anterior cruciate ligament repairs a 10 percent minimum to be graded upward with symptoms.
Id., p. 2.
¶ 61. The "Analysis of Proposed Rules" that was used for the creation of current Wis. Admin. Code § DWD 80.32 explains:
1. The conditions described in the rule cause permanent disability. By creating standards for evaluation the rule assures uniform payments for the same disabling conditions. .. .
*423. A minimum 5% permanent disability rating for removal of semi-lunar cartilage in the knee shall apply to all procedures. Physicians responding to the survey indicated that regardless of the type of surgical procedure performed there is a change in the anatomical structure of the knee justifying a 5% permanent disability rating for any procedure used. .. .
4. The rule pertaining to the knee is amended to include a minimum permanent disability rating for surgical repair to the anterior cruciate ligament. The physicians responding to the survey felt that a 10% disability rating is appropriate because there has been an interference, with the anatomical structure of the knee following the surgical repair.
Analysis of Proposed Rules, Rule No. Ind 80.32, Hearing Draft of Proposed Rules, DILHR, ii-iii (hereinafter "Analysis of Proposed Rules"). The "all procedures" addressed in paragraph 3 of the Analysis of Proposed Rules refers to whether the surgical procedure performed to repair a knee injury was a closed procedure8 or an open procedure. See O'Connell Memorandum, p. 2. Nothing in the Analysis of Proposed Rules implies that each time a repair is attempted for a single knee injury, the evaluating physician is to increase the percentage of disability.
¶ 62. In contrast, the Analysis of Proposed Rules could be read to suggest that when a back injury leads to a permanent disability each surgical procedure is to be awarded additional percentages of disability.
8. The rule pertaining to minimal permanent disability for the back is amended to clarify the permanent disability due for surgical procedures. A minimum 5% *43allowance will be given for every surgical procedure which is performed to relieve an individual from the effects of a disc lesion or spinal cord pressure.
Analysis of Proposed Rules, iii (emphasis added). A disability of the back, an unscheduled disability, was the only disability amendment made in the 1993-94 amendments that suggested a minimum disability allocation for "every surgical procedure which is performed," without regard to the disability that actually resulted. This difference is consistent with the comment of the Advisory Council that is shown at the subcommittee note for § DWD 80.32(11).
¶ 63. I could not find any explanation from the Advisory Council for the difference in treatment of a back disability as compared with the scheduled permanent disabilities that are also listed in Wis. Admin. Code § DWD 80.32. However, because a back disability is an unscheduled permanent disability, and as such it is not eligible for benefits absent proof of its effect on a claimant's earning capacity, Pfister, 86 Wis. 2d at 528, it is probable that the Advisory Council wanted to give physicians some assistance in tying the unscheduled permanent disability to loss of earning capacity.
¶ 64. However, whatever the Advisory Council's motivation, § DWD 80.32 was created to be, and remains, only a guideline that physicians who evaluate worker's compensation injuries are to consult. In addition, as we have explained, "LIRC cannot reject a medical opinion unless there is something in the record to support its rejection." Leist, 183 Wis. 2d at 460 (citing Erickson v. DILHR, 49 Wis. 2d 114, 181 N.W.2d 495 (1970)). Therefore, absent a concession by the employer, the values in § DWD 80.32 cannot override a physician's credible opinion based on his individualized *44evaluation of the worker's actual disability that resulted from a workplace injury. Id. at 459. Here, Dr. Ansari, May's treating physician, gave his medical opinion that May's permanent partial disability had not changed as a result of the second surgery. He said that May continued to have a 10 percent permanent partial disability due to the injury to his torn anterior cruciate ligament.9
C. Wisconsin Stat. § 102.18(1)(d)
¶ 65. The parties take differing views of the impact of Wis. Stat. § 102.18(l)(d) on the outcome of this case. DaimlerChrysler contends that the LIRC erred by stacking two minimum percentages from the administrative guidelines contained in Wis. Admin. Code § DWD 80.32, to accord May a 20 percent permanent partial disability. DaimlerChrysler contends that because the sole expert opinion in evidence opines that May has only a 10 percent permanent partial disability of his left leg at the knee, the LIRC's award contradicts § 102.18(l)(d). The LIRC and May contend that § 102.18(l)(d) does not preclude the LIRC's decision that May sustained a 20 percent permanent partial disability.
¶ 66. Wisconsin Stat. § 102.18(l)(d) states in relevant part:
*45Any award which falls within a range of 5% of the highest or lowest estimate of permanent partial disability made by a practitioner which is in evidence is presumed to be a reasonable award, provided it is not higher than the highest or lower than the lowest estimate in evidence.
I agree with the majority opinion's conclusion that Wis. Stat. § 102.18(l)(d) sets a range within which an award will be presumed to be a reasonable award. Majority op., ¶ 3. However, that conclusion determines only that there is no presumption of reasonableness for the 20 percent award the LIRC made because it is more than 5 percent higher than the highest physician's opinion in evidence.
¶ 67. The majority opinion does not answer the question presented here: Whether the LIRC erred in awarding benefits that are more than 5 percent higher than the highest medical opinion in evidence based on nothing except its interpretation of the guidelines for physician evaluations contained in Wis. Admin. Code § DWD 80.32(4), in the face of contrary, uncontradicted, credible medical testimony. I conclude that the LIRC erred because Dr. Ansari's opinion is uncontradicted, and it does not lack credibility. Leist, 183 Wis. 2d at 459. As I explained above, May has been Dr. Ansari's patient for many years. May repeatedly has been seen and evaluated by Dr. Ansari. Furthermore, the LIRC gave no reason why Dr. Ansari's opinion was insufficient to establish the existence and the extent of May's permanent partial disability.
¶ 68. By way of analogy, if May had incurred a second disability, for example from an injury to his back, he would have been required to provide proof of the existence and permanency of each injury, in order to receive a second permanent partial disability award. *46Wis. Stat. § 102.175; see Vande Zande, 70 Wis. 2d at 1093. In a like manner, because May had only one injury that resulted in a permanent disability, in order to receive a second payment for the functional disability of his left leg at the knee, he must provide proof that his knee has deteriorated further than the 10 percent disability for which he has already been paid.
¶ 69. The majority opinion never acknowledges that the cause and the extent of a disability under worker's compensation law are questions of fact that require substantial and credible evidence to support them. Wis. Stat. § 102.23(6). Instead, it repeatedly discusses the standard of review for statutory interpretation, a question of lav/ that has limited application here. See, e.g., majority op., ¶¶ 10-20. It also attempts to skirt the problem posed by uncontradicted, credible medical testimony that is contrary to the LIRC's factual finding by focusing on generalized policy statements about making an injured worker whole. Majority op., ¶ 32 n.14. The majority opinion reasons that it should sustain the LIRC's findings because, "The LIRC's decision recognizes that repeat or multiple surgeries have a cumulative, negative effect on function of the body part upon which they are performed." Id. While I do not contest that repeating medical procedures could increase the disability that those procedures were undertaken to remedy, in this case, there is uncontradicted, credible, medical testimony that May's disability did not increase subsequent to the second surgery. In my view, when the LIRC ignores that testimony, it makes a finding about the extent of May's injury that is not supported by credible and substantial evidence as Wis. Stat. § 102.23(6) requires; accordingly, the LIRC's factual finding should be set aside. Wis. Stat. § 102.23(6).
*47¶ 70. And finally, the LIRC has been inconsistent in its evaluation of knee injuries. In King v. DOT, WC Claim Nos. 2001-007515 and 2003-012619 (April 27, 2005), the LIRC reduced the extent of King's permanent partial disability attributed to a second workplace injury due to an earlier permanent partial disability finding for the same knee. This demonstrates that permanent partial disability of the knee has not been expanded procedure by procedure in other decisions by the LIRC. Similarly, in Hall v. DaimlerChrysler Corp., WC Claim No. 2001-037678 (April 15, 2004), the claimant had two knee surgeries after she injured her knee on January 6, 2000. She had a total knee replacement on March 6,2001 and a repeat surgery done on April 18, 2001. The minimum for knee replacement is 50 percent permanent partial disability, but her surgeon opined that a greater level of disability was present because of a loss of range of motion. He assigned 60 percent permanent partial disability. The employer argued that the extent of the disability should be reduced because the claimant had undergone arthroscopic surgery in 1997. In refusing that request, the LIRC said that there had been no work restrictions following the 1997 surgery and no permanent disability rating was assessed in 1997. However, the LIRC also did not make any allocation of permanent partial disability due to the April 18, 2001 repeat surgery. Instead, it relied on the opinion of her surgeon when setting the extent of her disability. Hall is consistent with the position of this dissent: it is the physician's opinion about the condition of the knee that drives the extent of the permanent partial disability rating that is assigned, unless the employer simply concedes to accept the minimum set in Wis. Admin. Code § DWD 80.32(4).
*48III. CONCLUSION
¶ 71. Because proof of the existence and the extent of a functional disability are factual issues to be determined when a scheduled permanent disability is under consideration and because the LIRC's factual determination is contrary to uncontradicted, credible medical evidence that the extent of May's scheduled permanent disability is 10 percent, the LIRC's decision is not supported by credible and substantial evidence and therefore is erroneous. Accordingly, I respectfully dissent.
¶ 72. I am authorized to state that Justices JON E WILCOX and DAVID T. PROSSER join this opinion.
In an autograft, tissue from another part of the patient's body is removed and employed to repair the patient's injury.
An allograft involves use of tissue that is taken from a source other than the patient's body, often from a cadaver.
Wisconsin Stat. § 102.23(6) states in relevant part:
If the commission's order or award depends on any fact found by the commission, the court shall not substitute its judgment for that of the commission as to the weight or credibility of the evidence on any finding of fact. The court may, however, set aside the commission's order or award and remand the case to the commission if the commission's order or award depends on any material and controverted finding of fact that is not supported by credible and substantial evidence.
Wisconsin Stat. § 102.44(4) states: 'Where the permanent disability is covered by ss. 102.52, 102.53 or 102.55, such sections shall govern; provided, that in no case shall the percentage of permanent total disability be taken as more than 100 per cent."
Wisconsin Stat. § 102.44(2) states in relevant part: "In case of permanent total disability aggregate indemnity shall be weekly indemnity for the period that the employee may live."
The LIRC did not overtly state that May's disability was scheduled; however, the calculation made in the LIRC's decision that is now under consideration demonstrates that the LIRC concluded that May incurred a scheduled permanent disability. To explain, the LIRC awarded 20 percent permanent partial disability, which it said equaled 85 weeks of benefits. The benefit weeks for a total scheduled disability of the leg at the knee is 425 weeks. Wis. Stat. § 102.52(11). Twenty percent of 425 weeks equals 85 weeks. By contrast, an unscheduled injury at 20 percent would equal 200 weeks, as 20 percent of 1000 weeks equals 200 weeks. Wis. Stat. § 102.44(3).
Wisconsin Stat. §102.13(1) requires an employee who seeks compensation for a work-related injury to submit to an employer's request for a reasonable medical examination by a *40physician of the employer's choosing. Refusal to submit to such an exam will result in the suspension of the employee's right to commence or continue an action for benefits under ch. 102. § 102.13(l)(c).
Closed surgery of the knee is done by arthroscopy.
Dr. Ansari opined that May initially had a 15 percent disability of his left leg, due to two distinct injuries to which Dr. Ansari attributed differing percentages of permanent partial disability. Dr. Ansari opined that May had a 5 percent disability caused by a torn meniscus and a 10 percent disability caused by a torn anterior cruciate ligament. May was paid for both permanent partial disabilities before the second surgery was performed on his anterior cruciate ligament. The 5 percent permanent partial disability from the torn meniscus was not a subject of this appeal.