purposes of $\S 287.220$. Rather, the courts have instructed that an occupational disease does not become a compensable injury until the disease becomes disabling. Garrone v. Treasurer of State, 157 S.W.3d 237, 242 (Mo. App. 2004). As the Garrone court explained:
An occupational disease does not become a compensable injury until the disease causes the employee to become disabled by affecting the employee's ability to perform his ordinary tasks and harming his earning ability. An employee can be diagnosed with an occupational disease and experience symptoms of the disease prior to the time that it becomes disabling.
Id. (citations omitted).
Here, employee twisted his left knee on October 10, 2000, but received only conservative treatment and went back to work without restrictions. (Employee worked light duty when he went back to work for employer, but the record does not show this was due to employee's knee condition, but rather suggests the light duty was related to employee's left shoulder, for which he underwent surgery in November 2000). After reviewing the medical record related to employee's bilateral knee conditions, we find the date of disability for the primary occupational disease to be July 5, 2006, the date employee underwent a left total knee replacement surgery, and the first time employee's earning ability was clearly and adversely impacted by his bilateral knee condition. Accordingly, for purposes of Second Injury Fund liability, we look at employee's preexisting conditions of ill on July 5, 2006, rather than October 10, 2000.
Employee underwent his last significant treatment for the bilateral shoulder condition in 2002. In our award in employee's claim for Injury No. 00-140019 (employee's claim for his bilateral shoulder condition), we have found that employee sustained a 40 % permanent partial disability of the left shoulder and a 25 % permanent partial disability of the right shoulder. We find that employee suffered these preexisting permanent partial disabilities and that they were serious enough to constitute hindrances or obstacles to employment on July 5, 2006.
Employee reached maximum medical improvement from the primary bilateral knee injuries on January 19, 2007, the last date he received treatment from Dr. Browne. We adopt the administrative law judge's ratings of 40 % permanent partial disability of each knee as our findings as to the nature and extent of disability resulting from the primary injury. Because we agree that employee is permanently and totally disabled as a result of the combination of his preexisting bilateral shoulder conditions and the primary injury in this matter, we affirm the award of permanent total disability benefits against the Second Injury Fund.