Except for the time Liddell punched the eyesight out of him.
Going blind has to count as an injury, right? 
-Chris Underground Blog 
He pulled out of the Gouveia fight with a wrist injury aswell.
Not to mention the pulled groin that he talks about in this very article. lol
Seriously though, it really is amazing how relatively injury free he's been with that insane number of fights.