Eugene Gunderman, 28, from Old Windsor in Berkshire, admitted stealing the Audi which knocked over PC David Oram in Chorleywood last July.
At St Albans Crown Court he was jailed for four years and ten months.
Damon Denham, 27, from Old Windsor, admitted car theft and was jailed for nine months.
Gunderman, of Queens Close, who also pleaded guilty to attempted robbery, ABH and dangerous driving, and disqualified from driving for five years.
Both men's sentences will run consecutively with convictions they received last August at Guildford Crown Court for their part in a conspiracy to rob a jeweller.
The court was told Denham drove Gunderman to Berkhamsted, in Hertfordshire, on 10 July.
Gunderman had arranged to test drive a grey Audi RS6, being advertised for sale, but instead sped off in it from the owner's home in Upper Hall Park.
Drivers on the M25 saw the vehicle racing along the hard shoulder at speeds of between 70 and 100 mph.
PC Oram and PC Stuart Fraser later found it parked in a lane where it was driven at them by Gunderman, who knocked down PC Oram, running over the base of his lower back and up his shoulder, before speeding off.
The defendants were arrested after the car collided with a number of other vehicles.
PC Fraser said he thought his colleague "had been killed".
"I have never been so relieved in my career to see someone get off the ground .... I have no idea to this day how he escaped," he said.
Mr Oram said his back was "never going to be 100 per cent" but hoped to remain as a front line officer as long as his back allowed.
Chief Supt Bill Jephson praised both officers for continuing to pursue the defendants, despite Mr Oram's "significant injuries".
"This proves how dedicated our officers are in facing life-threatening situations in order to prevent crime and protect the public, and their bravery should be commended," he said.
Two men have been jailed after they stole a car which was used to run over a Hertfordshire police officer, leaving him seriously injured.