EMPLOYEE WAS CARRYING OXYGEN TANK FROM SLED TO CROSSCUT OUTBY TO STORE WITH OTHER TANKS, WITH TANK ON LEFT SHOULDER HE STEPPED INTO A DEEP MUD HOLE. HE FELT SOMETHING TEAR IN HIS LEFT KNEE AS HE WAS TRYING TO GET OUT OF THE HOLE. *NOTE: EMPLOYEE LAST DAY OF WORK WAS 9/18/03.