The Lions have been using Theo Riddick as their starting running back after second-year player Ameer Abdullah injured his foot.
Forsett, 30, has been looking for employment since the Ravens released him last Tuesday. He and the Ravens said it was a mutual decision to part ways after Forsett dropped down the depth chart and was inactive for the team's fourth game of the season, a 28-27 loss at home against the Oakland Raiders.
In three games, all starts, Forsett rushed for 98 yards on 31 carries this year.
Last season he finished with 641 rushing yards after breaking his right arm in the team's 10th game.
The best year of his career, by far, was 2014, when Forsett replaced Ray Rice and amassed 1,266 rushing yards and eight touchdowns. Before that season, Forsett was a journeyman, making stops in Seattle, Indianapolis, Houston and Jacksonville.