After redshirting his freshman year with the Terrapins, Henderson missed the entire 2005 season after tearing his left anterior cruciate ligament.

Henderson entered his redshirt sophomore year in 2006 at Maryland and started 12 of 13 games at linebacker.

Henderson was a semi-finalist for the Dick Butkus Award, which went to James Laurinaitis of Ohio State.

He was suspended four games by the NFL on December 15, 2009, for violation of league's banned substances policy.

Set to become an unrestricted free agent for the 2013 season, Henderson re-signed with the Vikings for a two-year contract.

[10][11] Henderson was charged with a DWI and possession of ten grams of marijuana on February 27, 2014, after being released from the Vikings earlier that month.

[14] On September 29, 2017, it was announced that Henderson filed a lawsuit against the New York Jets for failing to accommodate his disability with his bipolar disorder and wrongful termination, which cost him more than $3 million.