Paramedics treating an assault victim on the side of a highway in Melbourne's east themselves became victims when he attacked them.

Police said officers were present about 8.40pm on Monday when the 29-year-old man being treated abused paramedics, hit one across the face and jumped from the ambulance.

The man struggled with police but he broke free and he ran across the west-bound lanes of the Maroondah Highway in Mooroolbark, a police spokeswoman said.

The man, from Bayswater, was hit by a car near the intersection with Edward Road and was taken to hospital with head injuries and a broken leg.

Police want any witnesses to phone Crime Stoppers on 1800 333 000.

An earlier version of this story suggested the attacker was 25 and from Morwell. The error was the result of incorrect information being given to the reporter.