Demby signed a contract with the Rams on Wednesday.
Demby was drafted in the sixth round by the Rams in April's draft, but was waived in mid-September, claimed by the Lions and subsequently ended up on their practice squad. The 22-year-old is still looking to make his NFL debut and should serve in a depth role for the Rams.
The Lions waived Demby on Tuesday.
Detroit claimed Demby off waivers after he failed to make it through the Rams' final roster cuts. He provided depth on the offensive line for two weeks, but failed to make an impact.
The Lions claimed Demby off waivers from the Rams on Tuesday, Tim Twentyman of the Lions' official site reports.
Demby, whom the Rams picked in the sixth round of April's draft, couldn't make the cut as a guard. He'll serve as a reserve lineman in Detroit.