Ravens coach John Harbaugh declared McClain out for the season Monday, but the roster move wasn't made officially until today.
Hamilton was signed by Baltimore to the practice squad after being cut by the Dallas Cowboys during the final major roster cutdown prior to the regular season.
Despite a solid preseason, Hamilton didn't stick with the Cowboys.
He battled knee and wrist injuries during training camp and fell victim to a numbers game in Dallas where DeMarcus Ware and Anthony Spencer are entrenched as the starting outside linebackers and the Cowboys drafted Kyle Wilber in the fourth round.
Hamilton broke Indianapolis Colts Pro Bowl defensive end Robert Mathis' Southwestern Athletic Conference single-season record with 20 1/2 sacks last season at Prairie View A&M.
Despite recording 81 tackles, six forced fumbles, being named a Football Championship Subdivision All-American and putting on a season-long hit parade captured in this highlight video, Hamilton went undrafted.
Hamilton is a 6-foot-3, 257-pounder with 4.6 speed in the 40-yard dash who began his collegiate career at Texas Tech before transferring to a junior college and then enrolled at Prairie View.