This would not be correct though, based on the CPT guidelines and parenthetical notes, which specifically state to use 20552 when no guidance is used. Not to be rude or disrespectful, but if the book says to use a certain code under certain circumstances, it doesn't really matter what was done, that's just what you use. The actual reason a trigger point code was selected instead of 20610 is because it's near impossible to hit the SI joint accurately without guidance. So the rationale is, if you're not using guidance, then you're not actually doing the SI joint injection, so you must be injecting the area around the joint, which would include the muscles. Does that make sense?