The team announced the move Wednesday to add depth after Goethel tore the ACL in his left knee in last week's loss in Baltimore.
Gaither has played in 77 games with 40 starts over six combined seasons with Philadelphia and Carolina. He spent training camp this summer with Houston.
Gaither has 393 career tackles, six sacks, 25 passes defensed, two interceptions, one forced fumble and two fumble recoveries in his career. He has experience playing middle and outside linebacker.