Each vertebra has four facet joints associated with it. They are located in the back of the spine. They are like any other joint in that they degenerate and get arthritis and can cause back pain. The problem is that there are many other structures in the spine which can cause back pain at the same time, but your brain cannot sort them out and tell you which one is causing the pain. The best and most reliable way to figure out where the pain is coming from is to selectively and precisely numb the joints and see if the pain stops or is greatly reduced. This is done with a very thin needle and X-ray guidance with or without sedation.