Purcell signed with the Broncos on Thursday after being released by the team on Tuesday, Aric DiLalla of the team's official site reports.
The move coincides with cornerback K'Waun Williams, safety P.J. Locke and tackle Alex Palczewski all being placed on injured reserve. Purcell played in all 17 games last season for the Broncos, registering 45 tackles (21 solo) and 1.5 sacks.