EMPLOYEE WAS MANUALLY LIFTING A 150 LB KNIFE GATE VALVE OUT OF A PICK-UP TRUCK. THE TAIL GATE DID NOT WORK SO HE AND HIS PARTNER HAD TO LEAN OVER IT TO PICK UP THE VALVE - TWISTING THEIR BODIES ON THE WAY TO THE GROUND, TO SET THE VALVE DOWN. EMPLOYEE DID NOT REPORT INJURY TILL 7:15 AM ON 8/10/04. *GIVEN LIMITED DUTY, MEDICATION, & PHYSICAL THERAPY X 6 VISITS BY MD.