A police officer sustained severe facial injuries requiring surgery as he tried to detain a suspect in South Gloucestershire.
It happened in Staple Hill on Tuesday night (20 August) and two people have been arrested.
The officer, who is 25 years old, remains in hospital in a stable condition.
Superintendent Pete Warren said:
The Police Federation told ITV News the incident highlights the dangers officers face while on duty.
The incident comes a week after an officer in Berkshire died while on duty, prompting tributes and a fundraising page which states:
"Police officers all over Thames Valley and the rest of the UK go to work each and every day to do their duty."
"We are courageous, caring and compassionate. We confront danger on a daily basis."