In Wieczorkowski v. Workers' Compensation Appeal Board (LTV Steel), 871 A.2d 884 (Pa. Cmwlth. 2005), the claimant sustained a right knee strain at work and was awarded total disability benefits. He subsequently entered into a supplemental agreement with his employer providing that "claimant's disability had resolved into a permanent partial disability and employer would remain responsible for all causally related medical expenses." Id. at 885. Four years later, employer filed a termination petition alleging full recovery. The Board affirmed the WCJ's decision, specifically holding that the parties' supplemental agreement did not bar employer from seeking to terminate benefits. This Court affirmed, and in doing so echoed the Supreme Court's analysis in Hebden v. Workmen's Compensation Appeal Board: We construe the plain unambiguous language of Section 413(a) to permit the termination of benefits recognized in a supplemental agreement at any time upon proof that the claimant's work-related disability has ceased. As our Supreme Court concluded in Hebden v. Workmen's Compensation Appeal Board (Bethenergy Mines, Inc.), 534 Pa. 327, 632 A.2d 1302 (1993), the principle of res judicata or issue preclusion only precludes a challenge to a claimant's current disability status where the claimant's condition is clearly irreversible, such as the case of a progressive occupational disease. Wieczorkowski, 871 A.2d at 887. See also City of Pittsburgh v. Workers' Compensation Appeal Board (Wiefling), 790 A.2d 1062, 1067 (Pa. Cmwlth. 2001) (noting that "a finding of a permanent disability is not the equivalent of a finding that the injury is irreversible.").