EE WAS LOADING A TRAILER WITH THE FORKLIFT. AFTER SETTING THE LOAD DOWN ON THE TRAILER EE STARTED TO BACK OUT, DIDN'T NOTICE THE WHEELS OF THE FORKLIFT WERE OFF THE GROUND. AS EE MOVED BACK, T HE WHEELS DROPPED TO THE GROUND CAUSING THE EE TO BE JOLTED AROUND IN THE CAB. RESULTED IN SEVERE BACK PAIN.