EE WAS WALKING PARALLEL TO THE TRACK LOCATION WHERE EMPLOYEES BOARD MANTRIPS. THE EE WAS GOING TO RETRIEVE A MANTRIP & NEEDED TO CROSS THE TRACK TO DO SO. WHILE ATTEMPTING TO CROSS THE TRACK, THE EE STEPPED ON TOP OF THE TRACK RAIL & SLIPPED. AS A RESULT, EE ""TWISTED"" HIS KNEE IN THE INCIDENT. EE'S FIRST LOST WORK DAY DID NOT OCCUR UNTIL 3/16/04 DUE TO SURGERY.