[1] The first issue before this Court is whether the Full Commission erred in finding that the provisions of G.S. 97-33 “show unequivocally that the defendants are obligated to pay only for the disability caused by this accident.”
The Industrial Commission is the sole arbiter of issues of fact. Hilliard v. Apex Cabinet Co., 305 N.C. 593, 290 S.E. 2d 682 (1982). Our review is limited to a determination of whether the Commission’s findings are supported by any competent evidence and whether its conclusions of law are supported by those findings. Id.
G.S. 97-33 provides:
If an employee is an epileptic, or has a permanent disability or has sustained a permanent injury in service in the army or navy of the United States, or in another employment other than that in which he received a subsequent permanent injury by accident, such as specified in G.S. 97-31, he shall be entitled to compensation only for the degree of disability which would have resulted from the later accident if the earlier disability or injury had not existed.
The purpose of the statute is to prevent double recovery. Pruitt v. Knight, 289 N.C. 254, 221 S.E. 2d 355 (1976).
In the case at bar, it is unclear whether the original knee replacement in 1977 was due to a chronic condition or was precipitated by a work-related injury during that year; the plaintiff and *191Dr. Vandersea gave different versions of its cause and the deputy commissioner did not resolve the issue in his findings of fact. However, Section 33 cannot apply on either view of the facts. Plaintiffs condition stems neither from epilepsy nor from an injury received in the armed services or in the course of other employment, and since plaintiff has received no compensation for the injury, his case does not fall within the provisions of Section 33. Pruitt, supra.
[2] In addition to its conclusion that G.S. 97-33 precluded recovery for more than 15% disability, the Full Commission adopted the deputy commissioner’s opinion in its entirety. Plaintiff assigns error to the deputy commissioner’s conclusion that plaintiff is entitled to compensation only for permanent partial disability in accordance with G.S. 97-31 and plaintiff asserts that he is totally disabled within the meaning of G.S. 97-29 and is therefore entitled to recovery under those provisions of the statute. We agree.
The threshold issue is whether G.S. 97-31 precludes recovery under any other provision of the statute. That Section provides in pertinent part:
In cases included by the following schedule the compensation in each case shall be paid for disability during the healing period and in addition the disability shall be deemed to continue for the period specified, and shall be in lieu of all other compensation, including disfigurement ....
(Emphasis ours.) In Perry v. Furniture Co., 296 N.C. 88, 249 S.E. 2d 397 (1978), our Supreme Court addressed the issue in a case where plaintiff had sustained a 50% loss of the use of his back and was “probably disabled from any useful occupation.” The Court found the phrase “in lieu of all other compensation” determinative and held that, where all of a plaintiffs injuries are included in the schedule set out in Section 31, he is “entitled to compensation exclusively under G.S. 97-31 regardless of his ability or inability to earn wages in the same or any other employment.” Id. In Fleming v. K-Mart Corp., 312 N.C. 538, 324 S.E. 2d 214 (1985), the Court made inroads into its rule in Perry, but the question was not squarely presented until the recent case of Whitley v. Columbia Mfg. Co., 318 N.C. 89, 348 S.E. 2d 336 (1986). There plaintiff had permanent partial disability of both hands and *192was totally disabled as a result. The Supreme Court discussed the history of the “in lieu of’ clause, and found that it was originally enacted to prevent compensation for both loss and disfigurement of body parts. The Court reasoned that allowing recovery under Section 29 posed no conflict with the fundamental premise behind that provision, and indeed furthered the purpose of the Act itself to compensate for lost earning ability. Thus, the Whitley Court held that Section 29 “is an alternative source of compensation for an employee who suffers an injury which is also included in the schedule” and ruled that the worker may select the more favorable remedy. Perry was overruled to the extent that it held otherwise. Following Whitley, we hold that plaintiff is not limited to recovery under Section 31.
[3] We now consider whether plaintiff is entitled to recover for total disability under Section 29. Plaintiff contends that the deputy commissioner erred in finding plaintiff to be permanently partially disabled and in apportioning plaintiffs award on the basis of the disability ratings assigned to the two knee injuries. Plaintiff argues that the accident materially aggravated his pre-existing infirmity such that he is now totally disabled and contends that he should recover for the entire extent of that disability. We first consider the extent to which plaintiff is disabled.
Section 29 provides in pertinent part:
Except as hereinafter otherwise provided, where the incapacity for work resulting from the injury is total, the employer shall pay or cause to be paid, as hereinafter provided, to the injured employee during such total disability a weekly compensation equal to sixty-six and two-thirds percent (662/s°/o) of his average weekly wages, but not more than the amount established annually to be effective October 1 as provided herein, nor less than thirty dollars ($30.00) per week.
In cases of total and permanent disability, compensation, including reasonable and necessary nursing services, medicines, sick travel, medical, hospital, and other treatment or care of rehabilitative services shall be paid for by the employer during the lifetime of the injured employee. If death results from the injury then the employer shall pay compensation in accordance with the provisions of G.S. 97-38.
*193The term “disability” is itself defined in Section 2(9):
(9) Disability. —The term “disability” means incapacity because of injury to earn the wages which the employee was receiving at the time of injury in the same or any other employment.
Courts interpreting the meaning of disability have emphasized that diminished earning capacity, and not physical infirmity, is used to gauge disability. Anderson v. Motor Co., 233 N.C. 372, 64 S.E. 2d 265 (1951). In Little v. Food Service, 295 N.C. 527, 246 S.E. 2d 743 (1978), plaintiff suffered a fall in the course of her employment. Her physician testified at the hearing that spinal cord damage from the fall resulted in incomplete use of her extremities, He rated plaintiffs physical disability at 50% and further testified that plaintiff was “wholly incapable of resuming her former employment as a laborer.” Another doctor testified that plaintiff suffered a 40% disability to the neurological system. He also estimated that there were “some gainful occupations that someone with this degree of neurological problem could pursue.” The presiding deputy commissioner found that plaintiff had suffered 45% permanent partial disability and awarded her a percentage of her weekly salary for 135 weeks pursuant to Section 31(23). The Full Industrial Commission and the Court of Appeals affirmed, and plaintiff petitioned for certiorari to the Supreme Court.
Writing for a unanimous court, Justice Huskins found no support for the conclusion that plaintiff suffered no more than a 45% loss of the use of her back. The evidence was uncontradicted that the damage to the nervous system affected all her extremities with loss of sensation. The Court remanded the case, holding that an award must compensate a claimant for all injuries received in an accident. Id.
The Little Court also addressed issues likely to recur in further proceedings. Emphasizing that the appropriate criterion for determination of disability is a finding of plaintiffs own incapacity for work, the Court found that the Commission erred in relying on a statement by one of the physicians that “there are some gainful occupations that someone with this degree of disability could pursue”:
*194Uncontradicted evidence establishes that she is over fifty years of age, somewhat obese, has an eighth grade education, and at the time of her accident had been working as a laborer earning less than $2.00 per hour. The relevant inquiry under G.S. 97-29 is not whether all or some persons with plaintiffs degree of injury are capable of working and earning wages, but whether plaintiff herself has such capacity.
Id. In the case at bar, the deputy commissioner found as a matter of law that plaintiffs total permanent physical impairment of the left leg is 45%. The deputy commissioner made no finding as to plaintiffs disability to earn wages; rather, he made the award on the basis of Dr. Vandersea’s rating of 15% permanent partial disability of the left leg. However, Dr. Vandersea testified as follows:
Q. ... do you have an opinion satisfactory to yourself with a reasonable degree of medical certainty as to whether or not Mr. Wilder would be totally disabled to work at a laboring type job?
Mr. Hedrick: Objection.
The COURT: Overruled. You may answer.
A. Yes, sir, I do have an opinion.
Q. (Mr. Weeks) And what is your opinion?
A. My opinion is he is totally disabled from that type of work and probably all gainful work that he’s qualified.
This uncontroverted evidence establishes that plaintiff—whom the court found to be 59 years old and to have a third-grade education—is totally disabled within the meaning of the statute. Although the impairment rating of his left leg is only 45%, that figure, as the Little Court pointed out, is not dispositive of the question of disability to earn wages. The evidence showed plaintiff to be totally and permanently unable to earn the wages he was receiving at the time of his injury. We now consider whether and to what extent plaintiffs 1983 work-related injury caused his disability.
[4] In Anderson v. Northwestern Motor Co., supra, our Supreme Court first addressed the issue of disability compensation where a *195prior condition and a work-related injury combine to disable a claimant. The Court held that, where the claimant
. . . suffers a personal injury by accident arising out of and in the course of his employment, and such injury materially accelerates or aggravates the preexisting disease or infirmity and thus proximately contributes to the death or disability of the employee, the injury is compensable, even though it would not have caused death or disability to a normal person.
Id. As the parties in the instant case have apparently agreed that the 1983 injury arose out of and in the course of plaintiffs employment, we do not address that issue here, but move directly to the question of causation.
Whether the injury materially aggravated the existing infirmity is once again to be determined with reference to the claimant’s capacity or incapacity for work. Just as a medical disability rating may be apportioned between two causes, so may the degree of incapacity to work be a function of two completely separate causes. As Judge, later Justice, Britt noted in Pruitt v. Knight Publishing Co.:
There is a distinction between a preexisting impairment independently producing all or part of final disability, and a preexisting condition acted upon by a subsequent aggravating injury which precipitates disability.
27 N.C. App. 254, 218 S.E. 2d 876 (1975), rev’d on other grounds, 289 N.C. 254, 221 S.E. 2d 355 (1976). This principle was later relied upon in Morrison v. Burlington Industries, 304 N.C. 1, 282 S.E. 2d 458 (1981), to award a claimant recovery for only part of her total disability. In that case, plaintiff contracted byssinosis as a result of her employment with Burlington Industries; she also suffered from such non-work-related conditions as phlebitis, varicose veins and diabetes. The Industrial Commission found that 55% of plaintiffs ability to work and earn wages was due to her lung disease caused at least in part by her employment, with the remaining 45% caused independently by her other infirmities. Despite some evidence to the contrary, the majority of the Court affirmed the decision of the Commission, citing testimony by two doctors that at least half of her incapacity to work —as opposed to *196her medical disability rating—was independent of her work-related problems and not aggravated by them.
The Morrison Court, however, was careful to distinguish the case before it from previous holdings. One situation beyond the scope of its narrow holding was set out by the Court as follows:
(2) When a pre-existing, nondisabling, non-job-related condition is aggravated or accelerated by an accidental injury arising out of and in the course of employment or by an occupational disease so that disability results, then the employer must compensate the employee for the entire resulting disability even though it would not have disabled a normal person to that extent.
Id. In such a case, where an injury has aggravated an existing condition and thus proximately caused the incapacity, the relative contributions of the accident and the pre-existing condition will not be weighed. Anderson v. A. M. Smyre Co., 54 N.C. App. 337, 283 S.E. 2d 433 (1981).
In the case at bar, the only medical testimony was that given by Dr. Vandersea. He testified that the disability rating to plaintiffs left leg was 45%, with 15% attributable to the 1983 injury, but that his incapacity for work was total. Although Dr. Vander-sea never specifically testified as to the relative contributions of plaintiffs 1977 and 1983 conditions to his incapacity to work, his testimony indicates that the 1983 injury materially aggravated the earlier one. Dr. Vandersea stated that there is a greater risk of damage with the new prosthesis than there would be were it plaintiffs first replacement. This likelihood was due in part to the extra bone damage during the second surgery. In addition, Dr. Vandersea testified that, if the damage were to recur, replacement of the prosthesis might —depending on the damage to the bone —be impossible and amputation would be necessary. That the 1983 injury materially aggravated plaintiffs condition is further shown by the fact that plaintiffs job performance was unaffected by the 1977 injury; after a 6-month healing period, he returned to his original duties and performed them satisfactorily until his injury some six years later. Thus, the evidence clearly indicates that plaintiffs 1983 injury aggravated a latent condition and therefore proximately contributed to his total disability. Although a normal person may not have been disabled to that ex*197tent, the entire disability is compensable. See Anderson v. Smyre, supra.
Because the Industrial Commission failed to take into consideration the abundance of uncontradicted evidence that plaintiff is permanently and totally disabled and that this disability was the result of a work-related injury which aggravated an existing infirmity, we remand the case for further proceedings in accordance with this opinion.
Reversed and remanded.
Judges Martin and Parker concur.