This meme has caught fire recently with the popularity of the game The Elder Scrolls V: Skyrim, so here’s the origins if you randomly see/hear this phrase and are wondering what it is.
“In The Elder Scrolls V: Skyrim, the town guard non-player characters (NPCs) have several stock lines they will repeat when the player walks near them, including the confession “I used to be an adventurer like you, then I took an arrow in the knee.” The restating of such a specific story over and over again by so many different guards caused it to be noticed by players, who then proceeded to post about it in gaming forums and image boards.” – Know Your Meme.
Also, a romantic comedy called The Five Year Engagement (out April 27), which was filmed before the Skyrim meme caught on, has a girl taking an arrow to the knee. Or, as suggested many times over, the producers decided to film the scene after learning of the reference from Skyrim and include it in the trailer to boost the movie’s popularity, as Skyrim is one of the most popular games of 2011 and will carry strongly into 2012.
(Check the YouTube comments, non-stop arrow to the knee responses.)