The 25-year-old Polk had his tender rescinded by the Eagles on April 24, making him an unrestricted free agent. He carried the ball 46 times for 172 yards and four touchdowns last season. Polk signed with Philadelphia in 2012 as an unrestricted free agent out of the University of Washington.
He'll join Houston's stable of runners with Arian Foster, Alfred Blue and Jonathan Grimes.
Polk was left searching for a new home after the Eagles signed DeMarco Murray and Ryan Mathews in free agency.