40 ILCS 5/12-144

An employee in receipt of any disability benefit shall undergo a medical examination periodically and in any event at least once each year by a physician designated by the board. Should the board decide as the result of such examination that the employee is no longer disabled for the performance of duty, the board shall discontinue payment of benefits. Should the employee refuse to submit to such examination, benefit payments shall cease and written notice thereof shall be given the employer by the board.