The NFC West side claimed the wide receiver off waivers yesterday.
The 23-year-old spent much of the 2012 season out of favour at the Lions for disciplinary reasons.
Young missed part of the off-season last year after being sent home for punching a teammate, before getting into an argument with the receivers coach for lining up in the wrong position on purpose.
Young recently tweeted that he did not want to play for the Lions if he did not get the ball more often.
Several of the Rams' starting wide receivers are set to become free agents during the off-season.