The sacroiliac joint is a common cause of low back pain.  It usually occurs after lifting a heavy object or putting a strain on the joint.  The sacroiliac joint can be afflicted by a number of disease processes including osteoarthritis, rheumatoid arthritis and ankylosing spondylitis.  The pain is localized to the lower back, but may radiate to the hip or leg.  The pain is worsened by activity and relieved by rest.  There may be tenderness to touch over the joint itself.  There are numerous provocative tests such as Patrick’s test, Gaenslen’s test and Yoeman’s test that can be used to discern if the pain is coming from the sacroiliac joint.  X-rays can be useful to exclude other bony causes of pain.  Laboratory test are used to detect inflammatory causes of pain.  If the pain is not clearly due to sacroiliac joint dysfunction, an MRI of the lumbar spine and bone scan will be necessary to exclude other causes such as a herniated disc, facet disease or other disorders of the spine.  The treatment of sacroiliac joint pain begins with conservative modalities such as heat, ice, rest and physical therapy.  Non-steroidal anti-inflammatory medications are helpful for pain control.  In patients who do not respond to conservative treatment, an injection into the joint under X-ray can provide pain relief.