EE WAS WALKING ACROSS UNIT 4 SECTION WHEN HE STEPPED ON A ROCK & TWISTED KNEE. CON'T TO WORK AND WAS SEEN BY DR OVER NEXT FEW MOS. LAST VISIT WAS 7/2/04. EE WAS NOT TREATED AGAIN UNTIL 3/7/05 HIS KNEE LOCKED UP JUST STANDING AND AT HOME. THIS IS NOT A NEW EVENT. BECAME A LOST TIME INJURY 6/2/05 FOLLOWING SURGERY ON RIGHT KNEE TO REMOVE SOME CARTILAGE.