40 ILCS 5/11-157

Proof of duty or ordinary disability shall be furnished to the board by at least one licensed and practicing physician appointed by the board. The board may require other evidence of disability. Each disabled employee who receives duty or ordinary disability benefit shall be examined at least once a year by one or more licensed and practicing physicians appointed by the board. When the disability ceases, the board shall discontinue payment of the benefit, and such employee shall be returned to active service.