A Northumbria Police officer was knocked unconscious after responding to a report of trouble at a party.
The female officer was taken to hospital following the incident at Byker Community Centre, Newcastle, in which another officer was also assaulted.
Police had been called to the party at just after 9pm on Saturday after a report of problems with a group of males who had been asked to leave the site.
A spokesman for the force said: "Upon arrival a number of those in attendance became aggressive and two of our officers were assaulted.
"One of those was a female police constable, who was knocked unconscious."
Two men and one woman were arrested after the incident and remain in police custody.
The officer has since been released from hospital and an investigation into the disorder has been launched.