The two officers were en route to Chino Prison with a parolee who had violated his probation.
According to Buena Park police, Caltrans had closed most of the lanes on the 91 for roadwork and traffic was at a crawl. That's when the truck rear-ended the patrol car.
The officers were treated and released at the scene for complaints of back and neck pain. The parolee was taken to an area hospital for complaints of back injuries.
City News Service contributed to this report.