EMPLOYEE RELATED THAT THE STEP ON THE LOADER GAVE-WAY WHEN EXITING FOR LUNCH. HE FELL APPROX. 4-4.5' & ROLLED ONTO HIS BUTTOCKS & BACK. FALL AGGREVATED PRIOR BACK INJURY. DR. PRESCRIBED PAIN KILLER, HEAT & PHYSICAL THERAPY. RETURN TO WORK ONLY AFTER MRI. PATIENT REFUSED DRUG TEST PER DRUG FREE PROGRAM.