The vehicle left along Walderslade Road in the direction of Wayfields at high speed.
The victim was taken to Medway Maritime Hospital where he was treated for broken ribs.
North Division's Detective Constable, Mark Silk, said: "This is a serious incident where the injuries could have been a great deal worse.
"Any information will be treated in the strictest confidence and we are interested in speaking to a white man in a brown tracksuit who left the vehicle prior to the incident."
Officers have also released a description of the driver. The victim reported that he is black, in his mid 20s, slim build with black short hair and a fine moustache. He was wearing a green checked shirt.
Anyone with information is urged to contact DC Mark Silk on 101 quoting reference XY/029479/12 or Kent Crimestoppers on 0800 555 111.