Paramedics treated the unidentified officer at the scene, then took him to the hospital.
The extent of his injuries is unknown, but he was moving his hands and legs.
The investigation shut down traffic during the busy morning commute, but all lanes have since reopened.
The accident occurred about 8:20 a.m. west of State College Boulevard, the California Highway Patrol reported.
The officer, assigned to the LAPD's South Traffic Division, was taken to a hospital for treatment of injuries that were not life-threatening, said LAPD Officer Karen Smith of the Media Relations office. His name was not released.
The circumstances of the accident were under investigation.
City News Service contributed to this report.