The incident unfolded at about 2 a.m. Sunday when the trooper pulled over a vehicle for a traffic stop near the intersection of Pacific Avenue and Pattison Street in Olympia.
As the trooper got out of his cruiser and was walking toward the vehicle to give the driver a ticket, another vehicle - a 1998 Nissan Altima - was heading west on Pacific toward the trooper.
The trooper saw the Nissan coming toward him. As the trooper jumped out of the way, he was struck on the arm by the mirror of the passing Nissan and knocked down. The Nissan kept going.
The trooper quickly recovered, jumped back into his patrol car and went after the fleeing Nissan. He followed it with flashing lights until the driver pulled about six blocks away, at Chambers Street and Pacific Avenue.
The driver of the Nissan, a 28-year-old Puyallup woman, tested positive for DUI, the State Patrol reported.
The trooper was later taken to the hospital as a precaution. He was treated for abrasions and released.
It was not immediately clear what became of the driver who was pulled over for the original traffic stop.