There are two types of facet joint injections: therapeutic ones (which relieve pain) and diagnostic ones (which find the source of the pain).
Facet joint injections are often used when the spine is damaged due to arthritis or injury and is causing pain anywhere along the spine or radiating outwards.
The injections may also be used to diagnose where pain is coming from by injecting anesthetic into space within a joint or directly into a nerve. If the injection within a joint helps, a steroid can be added to help more. If the injection directly into a nerve helps, another technique called a radiofrequency ablation may be used to block the pain signals along the nerve.