The Tennessee Titans have officially signed quarterback Chris Simms and activated veteran linebacker David Thornton off the physically unable to perform list, Jim Wyatt of The Tennessean reports.

Quarterback Vince Young has been placed on injured reserve, and first-year guard Ryan Durand has been placed on waivers to clear room on the 53-man roster.

An eight-year veteran, Thornton (6-2, 233) has been on the shelf after undergoing surgery on his hip and shoulder in the off-season. Since signing with the Titans in 2006, Thornton has 366 tackles, 2 quarterback sacks, and 2 interceptions in 58 games.

Thornton dramatically reduced his base salary, going from $4.35 million to $1.6 million, to remain with the Titans for the final year of his five-year contract.