A Pittsburgh police sergeant Friday sued a Beaver County man and the owner of Station Square over an injury the officer said he suffered there in 2009 while trying to break up a bar fight.

Sgt. Craig Campbell, head of the vice unit and a veteran of the city's elite Street Response Unit, was in uniform and working a secondary employment security detail at the Saddle Ridge bar on May 3, 2009, when a fight broke out in front of the nearby Matrix Bar at about 2 a.m.

When Sgt. Campbell responded to help other officers break up the fight, he said one of the combatants, Brian Richard Grimes, 27, of Beaver, kicked him in the knee from behind.

Police arrested Mr. Grimes and hauled him to jail.

Sgt. Campbell said he suffered a torn knee ligament and dislocated kneecap that has required surgery and extensive physical therapy.

In the complaint, filed in Allegheny County Common Pleas Court, Sgt. Campbell accused Mr. Grimes of assault and battery and Forest City Enterprises of negligence.

He said Forest City, owner of Station Square, was partially liable because the company didn't hire enough security personnel to handle brawls on busy nights, putting him at risk. According to the complaint, Forest City failed to provide adequate security despite knowledge of "heightened frequency of fights" on weekends.

The sergeant is seeking unspecified punitive damages. His lawyer didn't return a message Friday.

Forest City said it hadn't seen the complaint and doesn't comment on pending litigation.

Mr. Grimes was charged after the bar incident with various offenses, including aggravated assault and resisting arrest. His trial last month ended in a mistrial and a new one is coming up in the next several months, said his lawyer, Michael O'Day.

Sgt. Campbell, regarded as an aggressive officer, has been involved in several high-profile incidents in recent years. While a member of the response unit in 2005, he lost a finger in a gun battle with a Penn Hills man, Steven Hamlin, who died in the exchange.

Two years later, Sgt. Campbell shot and killed Michael Lee Ghafoor in Lawrenceville after police said he shook off a police dog and pointed a gun at officers during a foot chase.