On a 2011 it probably doesn't have a swing arm, but you could probably mount one. There's probably a piece of wood trim along the top edge of the TV with 3 screws holding it in place. If you remove that trim, and feel for a locking screw behind the TV's bottom edge, and loosen it, you can pull the bottom edge away from the wall and lift up to take the TV off the mounting brackets. Once you have it off, I would think you could replace the fixed mount with an articulating mount.
It'll be handy to have a 2nd person help because there are power and signal cables attached that will have to be managed.
