Hundreds of football fans attacked police officers as violence broke out after Sunday's FA Cup tie between Stoke City and Birmingham City.
Police were attacked by rival fans outside the stadium
Trouble began at the Britannia Stadium when a group of about 200 visiting fans ripped down fencing separating them from Stoke supporters.
As rival gangs left the ground, police faced what a senior officer described as "extreme violence".
Several arrests were made and officers are studying CCTV images.
Mounted officers and dog handlers were among those attacked by fans of both clubs outside the stadium, and police had to close the nearby A50 as they dispersed the crowd.
The match commander, Supt Andy Franks, said: "Our officers prevented serious disorder between the rival groups of hooligans and a number of arrests have been made in and around the stadium.
"Those officers were faced by extreme violent behaviour from a significant number of criminals.
"Those arrested will be questioned by detectives this evening and further arrests are likely."