The sacroiliac joints, also called SI joints, connect the sacrum to the iliac bones on each side. The sacrum is the triangular bone below the lumbar spine and the iliac bones are the two large bones that form the pelvis. The SI joint consists of strong ligaments that permit limited motion. The SI joints support the full weight of the body when a person stands. The substantial stress can erode the cartilage of the joints and lead to arthritis. Sacroiliac joint dysfunction, or sacroiliitis, simply refers to inflammation of the SI joint due to any cause, resulting in pain.
Diagnosis sacroiliac joint dysfunction starts with a careful and detailed history and physical exam. The physician will feel for tenderness over the SI joints, legs, hips, spine, and gluteal region. She or he may put gentle pressure on the SI joint to try to reproduce the pain. Neurologic tests are used to assess muscle weakness. Pain from SI joint dysfunction can mimic the pain associated with other lower back conditions such as herniated disks, confounding the diagnosis. The SI joint often appears normal on diagnostic imaging studies such as X-rays.
Injecting the sacroiliac joint with local anesthetic can be used as a provocative test. If the pain diminishes after the injection, it can confirm the SI joint as the source of pain.
Non-steroidal anti-inflammatory medications such as ibuprofen and naproxen may be effective. Physical therapists can teach stretching and stabilizing exercises to help reduce SI joint pain. Pilates and yoga can help as well. Steroid injections into the sacroiliac joint, often with radiographic guidance, can be performed if more conservative therapies do not provide relief. Surgical fusion of the SI joint is used as the treatment of last resort to relieve symptoms.