I am sure that I am overthinking this and making it harder on myself. Our physician states in her note "Left and Right SI joint injection administered to lumbar". I realize that 20552 states 1 or 2 muscles and 20553 states 3 or more muscles. Since the physician stated Left & Right injection I coded this case using 20552-RT, 20552-RT-59. It was denied by carrier. Of course my only other selection left is 20553. I just want to make sure that I am understanding the usage of these two codes as I am thinking lumbar has two separate locations (Left & Right). Thank you in advance for any help with this matter.