The team did not release additional terms of the deal Thursday. Swanson, a center who played at Arkansas, was taken with the 76th overall pick.
The Lions added Swanson to give themselves depth behind Dominic Raiola, who has been with them since 2001. Eventually, Swanson could be Raiola's replacement.
Swanson was one of six finalists for the Rimington Trophy, which is awarded to college football's best center.
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