Facet joints are small joints at each segment of the spine that provide stability and help guide motion. The facet joints can become painful due to arthritis of the spine, a back injury or mechanical stress to the back. A cervical (neck), thoracic (upper back) or lumbar (lower back) facet joint injection involves injecting a steroid medication, which can anesthetize the facet joints and block the pain. The pain relief from a facet joint injection is intended to help a patient better tolerate a physical therapy routine to rehabilitate his or her injury or back condition.