THE DRIVER WAS ATTEMPTING TO CLOSE THE SLIDING WINDOW ON THE WATER TRUCK FROM THE SEAT & AFTER BEING JAMMED ON THE 1st ATTEMPT, PULLED HARDER ON THE 2nd ATTEMPT & THE WINDOW BECAME FREE & THE DRIVER LOST HIS BALANCE & FELL OUT OF THE CAB ONTO THE GROUND LANDING ON HIS FEET & THEN FELL FORWARD ONTO A PALLET OF SCREEN CLOTH CUTTING HIS LEFT KNEE.