EE WAS STANDING ON C12 CATWALK WORKING ON DUST COLLECTOR DUCTWORK WHEN HE TURNED AROUND, STEPPED ON LOOSE ROCK ON THE CAT WALK CAUSING HIM TO TWIST HIS RIGHT KNEE. THE KNEE DID NOT IMPROVE AND EE WAS SENT TO ORTHOPEDIC WHO PERFORMED DIAGNOSTIC ARTROSCOPY ON 10-18-00 THUS MAKING INJURY REPORTABLE.