THE EE WAS ROCK BOLTING STANDING ON MUCK PILE OFUNEVEN MATERIAL. HE STEPPED BACK TO PULL THE BOLTER OUT OF THE HOLE ONTO A ROCK & TWISTED HIS RIGHT KNEE. HE REPORTED THE INJURY TO HIS SUPERVIS OR BUT DID NOT GO TO DR UNTIL 1/17/01. HE RECD A FULL DUTY RELEASE TO RETURN TO WORK WE WERE UNAWARE HE WAS CONTINUING TO HAVE PROBLEMS WITH HIS KNEE UNTIL WE WERE NOTIFIED ON 5/4/01 BY WORKE