Ontario's police watchdog says they are satisfied an officer who arrested a woman resulting in her sustaining "serious" injuries didn't commit a criminal offence.

Special Investigations Unit director Tony Loparco says the arrest of Maria Farrell on April 2, 2013 by OPP Sgt. Russell Watson was lawful and he did not use excessive force.

The SIU says Farrell was arrested on Colborne Street East in Orillia after an altercation with Watson who was responding to a report of an assault in the area.

She sustained injuries including a fractured left tibia as the two struggled during the course of the arrest.

Watson was originally cleared of any criminal offence in May 2013 after the SIU concluded there were no grounds to believe he used excessive force.

The SIU says it reopened the investigation in March after a judge made critical comments of the officer in the case against Farrell for obstruction and assaulting a police officer that resulted in her acquittal.