EE WAS MOVING A BELT GUARD DOWN THE SLOPE. HE STEPPED ON LOOSE COAL CAUSING HIM TO LOSE HIS FOOTING AND SLIP. HE TWISTED HIS LEFT KNEE. SLOPE ANGLE IS 16 DEGREES. THIS ACCIDENT WAS FIRST TREAT ED AS A FIRST AID CASE. EE WAS NOTIFIED ON 8/22 THAT SURGERY IS NOW REQUIRED WITH LOST TIME AS ARESULT.