Knockout Reilly.

A Malcolm St. Clair silent boxing sports romantic love triangle prison melodrama about a steel worker who saves a girl in a bar fight by knocking out the man coming on to her. It turns out the man was a boxer named "Killer"; so our steel worker becomes a boxer, but is then arrested for a crime he didn't commit. While in prison, he continues training, so that when he gets out, he can fight "Killer"; he is losing the fight, but his girl tells him that "Killer" framed him, which gives him the drive to knock his opponent out in the final round!