Petitioner Eugene Seabolt seeks review of a Police and Firemen’s Retirement and Relief Board decision denying him disability retirement. The Retirement Board found that petitioner was injured in the performance of duty under D.C.Code 1973, § 4-527, but concluded that he was not “disabled for useful and efficient [service] in the grade or class of position last occupied,” under D.C. Code 1973, § 4-521(2). We affirm.
On appeal, petitioner claims that “[t]he threshold issue presented ... is whether [he] is permanently disabled for the performance of his fire fighting duties.” That contention is inaccurate for several reasons. First, this court may not indulge in a de novo factual determination of petitioner’s disability. Instead, the standard of review is whether there is substantial evidence in the record to support the Retirement Board’s unanimous finding that he was not disabled. D.C.Code 1978 Supp., § 1-1510(3)(E). See discussion and cases cited in Citizens Association of Georgetown, Inc. v. District of Columbia Zoning Commission, D.C.App., 402 A.2d 36, 41-42 (1979). Second, the permanence of petitioner’s disability is not at issue here, since the Retirement Board did not articulate it as grounds for its finding of nondisability. Finally, as we hold here, disability from performing the “fire fighting duties” associated with petitioner’s latest position with the depart*909ment does not, per se, constitute disability. Under D.C.Code 1973, § 4-521(2), petitioner must also be incapable of performing any “useful and efficient service” for the department in a position of the same “grade or class of position” as that he last occupied.
The record shows that petitioner, a sergeant in the District of Columbia Fire Department, was appointed in 1967. He injured his knee while playing a game at the firehouse basketball court on April 17, 1977. On April 22, surgery was performed to correct a torn meniscus and a rupture of the collateral ligaments in his knee.1 The prognosis for recovery from such surgery is fairly good; the Police and Surgeons Board representative at the hearing, Dr. Albert E. Rolle, testified that, upon removal of the meniscus, “the individual can go back . [and] can function at least reasonably well. Probably not 100 percent, but close enough that he can engage in any occupation.”
After his leg cast was removed on June 7, petitioner began a program of physical therapy. He returned to work, on light duty status, on September 10, and performed this work without apparent difficulty until October 26, when he unexpectedly requested sick leave.2 Petitioner claimed his request was the result of his physician, Dr. Robert E. Collins, telling him, earlier that day, that he “would not ever go back to fire fighting.” There was also evidence that petitioner was scheduled to report that day to a new light duty assignment in the Apparatus Division, where a permanent, full-time sergeant’s position had become vacant.
On October 30, Dr. Collins wrote the Police and Fire Clinic that, although petitioner “was handling light duty OK,” he recommended petitioner be retired because “he won’t be able to handle regular duty.” The Board of Police and Fire Surgeons recommended that petitioner be found “permanently disabled for duty, not in the performance of duty.”3
Both Dr. Collins and Dr. Rolle testified that petitioner was disabled from performing active fire fighting duties.4 Dr. Collins testified that petitioner “does not have a competent left knee from the standpoint of what would be required in fire fighting duties,” and that his knee might be taxed by carrying heavy equipment or climbing ladders.
Dr. Rolle, on the other hand, testified that petitioner’s surgery “does not necessarily portend a disability,” saying: “We have many active policemen who have had men-iscectomies. We certainly see many athletes who have had meniscectomies try to bounce back and can certainly perform as though nothing had ever happened.” He also testified that petitioner’s post-operative chondromalacia,5 although permanent, did not preclude “any type of muscle building rehabilitative exercise.”6
*910The only objective evidence of petitioner’s disability (chondromalacia), other than the surgical scar, was noticeable crepitation (a phenomenon that Dr. Rolle said “does not necessarily produce . . pain”), chronic swelling of “a very mild degree,” and a slight reduction in the knee’s range of flexion (petitioner’s 105 degree motion was “almost normal — maybe a few degrees off . the normal knee should flex to about 115 degrees, and most of us don’t use the full degree of flexion.”). Dr. Rolle also testified that the medical record “doesn’t indicate that an examination was performed at [the] time [petitioner was placed on sick leave] so that I would conclude it was because the patient said that he had pain. Subjective.”
Petitioner testified that he had no trouble walking, driving, or mowing the lawn and said, “I have never taken anything for pain other than Aspirin or Bufferin.” He also said he could physically handle the work he did on light duty status and could have continued performing those duties. Dr. Collins concurred, testifying that petitioner “absolutely” could do office work: “There are many physical tasks that he can perform. He will have pain in the knee, but he will have that whether he works or not.”
There was, in short, ample evidence before the Board that, whatever disability petitioner suffered, it did not preclude light duty work. The question, then, is whether the ability to perform some limited duty position in the department prevents a disability finding under D.C.Code 1973, § 4-521(2).
Under Coakley v. Police and Firemen's Retirement and Relief Board, D.C.App., 370 A.2d 1345, 1349-50 (1977), the answer was clear. We held there, on similar facts to these, that petitioner’s ability to perform a “non-fire fighting” position in the department precluded him from disability retirement, upholding the Retirement Board’s interpretation of “grade or class of position” in § 4-521(2) as a “category defined by rank or salary, or both, e. g., Private . . .” Id. at 1348. We gave great weight to the Board’s rejection of petitioner’s argument that the phrase referred to “an occupational category defined by duties and responsibilities, e. g., fire fighter . . .,” id., stating that “where an administrative agency’s construction ... is reasonable and does not contravene the language or legislative history of the statute, it should be followed.” Id. at 1349 (quoting Harrison v. J. H. Marshall & Associates, Inc., D.C.App., 271 A.2d 404 (1970)). We also refused to adopt the gloss that federal courts have given identical language in the Federal Civil Service Retirement Act of 1926, on which our Police and Firemen’s Retirement and Disability Act Amendments of 19577 were expressly modelled,8 in the absence of any legislative history inconsistent with the Board’s interpretation of the plain language in § 4-521(2). Coakley v. Police and Firemen’s Retirement and Relief Board, supra at 1349.9 We noted that public policy favored the Retirement Board’s “[interpretation of] the retirement laws to discourage the retirement of District of Columbia pér-*911sonnel who, while disabled from the performance of certain duties, can perform useful and efficient service in other capacities within their respective departments without suffering any diminution in rank or salary.” Id.
Our opinion in Jones v. Police and Firemen’s Retirement and Relief Board, D.C.App., 375 A.2d 1 (1977), decided three weeks after Coakley, reiterated the proposition that a petitioner who could still perform the duties of a position at the same grade or class as the one last occupied (in Jones, the petitioner remained capable of performing the very same position she last occupied) was not disabled under § 4-521(2). We also rejected Jones’ reliance on the police department’s “new and current policy terminating light-duty status availability to persons injured off-duty,” id. at 4, and its rule that “every officer may be ordered to perform every kind of police task,” id., as conclusive proof that there was no longer any position in the department in which she could render useful and efficient service. We noted that, since the Board in Jones found she was capable of performing “the kind of tasks her last kind of job required, . it was unnecessary for the Board to address itself to the issue petitioner . raised on review [whether there were other jobs which petitioner could perform under the new regulations]. Obviously no regulations which are inconsistent with statutory objections can be accorded such effect.” Id. at 6.
Petitioner here implicitly relies on a similar departmental policy (included in the record as a memorandum issued by Fire Chief Jefferson Lewis, entitled “Limited Duty Assignments in the Fire Department”) to sustain his argument that incapacity from active fire fighting makes him disabled under § 4-521(2). The memorandum states that “[w]hen it is quite evident that one of our men cannot be rehabilitated to full duty fire fighting, then we do a disservice to the taxpayer if we continue that man on our rolls,” and that “[t]he Fire Department’s official position is that this department cannot employ [such a person] on a permanent basis . . .”
Noting, as did the Jones court, that the Act we are construing was enacted in 1957, “long before any of the changes in Departmental personnel policies to which petitioner has drawn our attention,” id. at 6, we must endorse that court’s conclusion that “It was plainly the premise of Congress in framing the disability provisions of this Act that not all police positions were interchangeable and that many officers were permanently assigned to nonphysically taxing jobs .... Any disability plan which would grant pensions to persons for injuries not diminishing their ability to continue to do such work would . be a tremendous waste of public funds.”10 Id.
Thus, until our recent opinion in Torvik v. Police and Firemen’s Retirement and Relief Board, D.C.App., 406 A.2d 1264 (1979), there was no question that a petitioner who could satisfactorily perform either his old job or another available light duty position of the same grade or class was not eligible for disability under § 4-521(2), notwithstanding departmental, policy or regulations to the contrary.
Although the dicta in Torvik, amplifying the “old job” dicta in Jones, supra at 6, and see note 10 supra, stated that “Congress was most explicit in defining the words ‘disabled’ or ‘disability’ in terms of the particular police job last held by the claimant,” its holding “would be the same,” as the opinion makes clear, “even if [it] were to rely on Coakley alone, ... as there was no evidence that there was any position in the police department that the petitioner *912was fully capable of performing.” Torvik v. Police and Firemen’s Retirement and Relief Board, supra at 1266. Strictly speaking, Congress did define “disabled” in the terms of the last job held by the claimant. However, the last job was merely a starting point that referred the Board to larger category of jobs — those in the same “grade or class” as that job. A petitioner must then establish disability from performing any job in the category before qualifying for retirement pay under § 4-521(2).
We, therefore, read Torvik for the limited proposition that, given the record in that case (showing that petitioner’s left hand had “essentially no rotation,” id. at 1265 n. 2, and that it disabled him from performing any job in the department), there was not substantial evidence under D.C.Code 1973, § 1-1510(3)(E) to support the Retirement Board’s finding of no disability. Thus, our opinions in Jones and Coakley remain undisturbed by Torvik.
A brief look at the clear language of § 4-521(2) should be sufficient to underscore the continued vitality of Jones and Coakley and rebut petitioner’s argument that the Retirement Board must determine disability solely on the basis of whether a petitioner can still fulfill the particular position he happened to occupy at the time disease or injury struck. Had Congress intended this standard, it could easily have said so, and defined disability in § 4-521(2) as “disabled for . . . service . in the last position occupied by the member.” It did not. Instead, it legislated that disability means “disabled for service in the grade or class of position last occupied by the member.”11 D.C.Code 1973, § 4-521(2) (emphasis added).
Since there was substantial evidence in the record before the Retirement Board here that petitioner could still perform light duty in a position of the same grade or class as the position he last occupied in the department (sergeant), we must affirm the Retirement Board’s conclusion that petitioner was not disabled under § 4-521(2), under the same standard we applied in Coakley, supra.12
So ordered.
. An arthrotomy and a meniscectomy (removal of the meniscus cartilage) were performed.
. Petitioner testified that he told his physician that he was doing “fine” on light duty and “figured . . . when [he] went back to the doctor [on October 26] . . . that [his doctor might] soon tell [him he] could go back to full duty.”
. The latter issue is not contested here since the Retirement Board found that the injury was incurred in the performance of duty, on the basis of evidence that the Fire Department had sanctioned the basketball games as on-duty recreational activity.
. For purposes of this opinion only, we accept as true the petitioner’s contention that he was incapable of active fire fighting.
. Dr. Rolle defined chondromalacia as a “thinning of the cartilage.” The term is used “to encompass degeneration and roughening as well.”
. On August 26, Dr. Collins said petitioner’s “knee straightened completely” and he “could start bike riding and jogging.” The implication in petitioner’s brief, which concludes, “ . the Board has forced genuinely disabled fire fighters, such as the petitioner, to either resign . . or to attempt to continue to work over the objection of their clinic physicians, which poses and [sic] unwarranted danger to their health” is misleading. There is no evidence in the record to support petitioner’s contention that his health would have been endangered by continuing light duty or any other work or activity, or that his physician ever objected to his continuing light duty work.
. House Rule 6517, enacted as Pub.L.No.85-157, 71 Stat. 391, 85th Cong., 1st Sess. (codified at D.C.Code 1973, §§ 4-521 to -538).
. Section 2 of the Police and Firemen’s Retirement and Disability Act Amendments of 1957 reads:
It is the intent of Congress in enacting the . Act Amendments of 1957 to give the members coming under such Act benefits substantially similar to benefits given by the Civil Service Retirement Act Amendments of 1956 to officers and employees covered by the Civil Service Retirement Act of May 29, 1930, as amended.
Section 401(1)(g) of the federal Act of 1956, Pub.L.No.854, 70 Stat. 744, is identical to D.C. Code 1973, § 4-521(2).
.In the phrase in the grade or class of position occupied by the employee, the emphasized portion was added in the 1926 Amendments to the Civil Service Retirement Act of 1920, 44 Stat. 904, 907, ch. 801, § 6. The word “last” was inserted between “position” and “occupied” in the 1956 Amendments to the Act, 70 Stat. 744, § 401(1)(g). As we said in Coakley v. Police and Firemen's Retirement and Relief Bd., supra at 1349: “[T]he legislative history of the 1926 Act does not disclose the precise meaning that Congress attached to the phrase, ‘in the grade or class of position.’ ”
. We do not, however, endorse the dictum in Jones that Congress intended “to limit disability pay to officers no longer capable of performing their old jobs.” Jones v. Police and Firemen’s Retirement and Relief Bd., supra at 6. That observation cannot be detached from the unusual factual context of Jones, particularly since it conflicts with the clear language of § 4-521(2), which looks, not to the petitioner’s ability .to perform his or her particular “old job” but rather to the ability to perform jobs of the same “grade or class of position” as the “old job.” See further discussion infra.
. We will not distort the grammatical syntax of this statute to reach an illogical result. Although the terms “position” and “last occupied” are'juxtaposed in the statute, the latter does not modify the former (which is merely the object of the preposition “of”). Both adjectival terms, instead, modify “grade or class.” Thus, we must turn to the category of jobs in petitioner’s grade or class of position to discover whether petitioner is able to render “useful and efficient service” to the department. Such a category includes, but is not exhausted by, the very job petitioner last occupied. See Jones v. Police and Firemen’s Retirement and Relief Bd., supra.
. We do not discuss our unpublished memorandum opinion and judgment in Tubbs v. Police and Firemen’s Retirement and Relief Bd. (No. 13425, Jan. 8, 1979), which is quoted at considerable length in respondent’s brief, because it is devoid of precedential value. District of Columbia Court of Appeals Internal Operating Procedures (1978), Rule IX-C.