Detroit signed Thomas off of the Bengals' practice squad Tuesday, Jeremy Fowler of ESPN.com reports.
Thomas suffered a significant knee injury sometime last week, Mary Kay Cabot of Cleveland.com reports.
Thomas participated in team drills Thursday, Zac Jackson of The Athletic reports.
Thomas (foot) has been ruled out for Sunday's game against the Steelers, Anthony Poisal of the team's official site reports.
Thomas (hand) is expected to practice this week and potentially available for Saturday's preseason game against the Bears, Chris Easterling of the Akron Beacon Journal reports.
Coach Stefanski said Tuesday that Thomas (hand) is expected to be sidelined for a few days, Scott Petrak of the Elyria Chronicle-Telegram reports.