Detectives are appealing for anyone who may have seen a man acting suspiciously in fields near the A5 after a police officer suffered serious injuries.
A 30-year-old man from Leicester is currently being questioned by police in connection with the incident at 6.15pm on November 29.
A Staffordshire Police officer was threatened by a HGV driver, causing him to step into the carriageway where he was hit by a passing vehicle.
But detectives are now searching for a second man who they believe was also in the lorry.
Detective Inspector Dan Ison said: “Did you see a man acting suspiciously near to fields to the side of the A5 in between Wall Island and Weeford Island?
“We are still appealing for witnesses and I would encourage anyone with any information to come forward and contact us.
“While we have made an arrest, the investigation is still very much ongoing and we are still looking for a second suspect.”
The 39-year-old officer has since undergone surgery for a serious leg injury.
Anyone with any information is asked to contact Staffordshire Police on 101 quoting incident 583 of 29 November.