EMPLOYEE WAS CLEANING WINDSHIELD ON LOADER WHEN HIS FOOT SLIPPED ON MUD/GREASE. HE GRABBED THE CAB FRAME TO STOP HIS FALL AND FELT MINOR PAIN IN LOWER BACK. PAIN WORSENED DURING THE DAY AND HE WAS SENT TO THE HOSPITAL FOR EXAMINATION. LUMBAR STRAIN/SPRAIN. HE WILL BE ON MODIFIED DUTY UNTIL NEXT EVALUATION, 20 SEPT. 04. EMPLOYEE ALSO TOLD TO CLEAN VEHICLE STEP SURFACES.