EMPLOYEE SQUATTED DOWN TO MOVE PLATE ON FLOOR AND WHEN HE TRIED TO SLIDE THE PLATE OVER, HE HEARD HIS KNEE POP. RECEIVED MEDICAL TREATMENT BUT NOT MSHA REPORTABLE. 9/4/04 EMPLOYEE WAS STEPPING UP IN PAN. WHEN HE PUT HIS WEIGHT ON KNEE IT STRAINED HIS KNEE. RECEIVED MEDICAL TREATMENT ON 9/7/04. MSHA REPORTABLE, EXISTING INJURY.