The six-year veteran, a second-round pick by the Vikings in the 2003 NFL draft out of Maryland, suffered the injury in the second quarter of Minnesota's 30-17 loss to the Tennessee Titans on Sept. 28.
In four games, Henderson, Minnesota's defensive anchor, compiled 27 tackles (23 solo), a forced fumble, and a sack and had missed only three games in his career.
"Every day, we go into our linebacker room and see his chair empty," fellow linebacker Ben Leber told the Saint Paul Pioneer Press. "It's kind of a weird feeling. We're all anticipating his return just to come back and be around us. We miss that already."
Henderson made a career-high 119 tackles with 4 1/2 sacks in the 2007 season.