I would expect this line to move closer to even. Henderson is 41, but in good physical condition. "Shogun" has gone through multiple surgeries on his knees. He moved, despite being victorious, poorly in his last fight in August. Henderson, who never been finished with strikes in his career, is more likely to finish the fight, and his wrestling poses a problem if the fight goes the distance as well.
"Shogun" closed as a -210 favorite for his last fight against Forrest Griffin at UFC 134. (He closed as a -265 favorite in the first fight at UFC 76.) Rua stopped Griffin by KO at 1:53 of round one.
Henderson closed as a +255 underdog in his last fight against Fedor Emelianenko at Strikeforce's event at the end of July. Henderson finished Emelianenko by KO at 4:12 of round one.