EE WAS OPERATING THE 801 EXCAVATOR REMOVING CLAY MATERIALS FROM A SPOIL BANK. AN UNKNOWN AMOUNT OF CLAY BROKE FLEE AND STRUCK THE FOREARD OPERATOR GLASS OF THE EVCAVATOR CAUSING IT TO SHATTER. THIS IN TURN IS BELIEVED TO HAVE CAUSED THE OPERATOR TO MAKE A SUDDEN MOVE INSIDE THE CAB AND STRIKE HIS LEFT KNEE AGAINST THE BRACE OF THE MACHINE RESULTING IN THE INJURY OF HIS LEFT KNEE.