EE WAS ASSISTING WITH CLEANING SPILLAGE IN THE ROADWAYS AND AROUND THE FEEDER. EE STATED THAT EE EXAMINED THIS AREA AND NO HAZARDS WERE PRESENT, BUT WHILE WALKING THROUGH A X-CUT, A PIECE OF BINDER FELL FROM THE RIB AND STRUCK EE LEFT KNEE. THIS WAS A GLANCING BLOW AND NOT A DIRECT HIT. X-RAY WAS NEGATIVE.