Sacroiliac (SI) joint injury is a common cause of low back pain. Posterior pelvic joint pain a common name for SI joint dysfunction. The spine and pelvis are connected by the sacroiliac joint. The SI joint lies between the iliac’s articular surface and the sacral auricular surface. When an injury occurs to the SI joint, patients often experience significant pain in their low back and buttock region. The SI joint experiences forces of shearing, torsion, rotation, and tension. Ambulation is heavily influenced by the SI joint, as this is the only orthopedic joint connecting our upper body to our lower body. The joint is a relatively stiff synovial joint filled with synovial fluid. The bones of the sacrum and ilium are coated in hyaline cartilage at their articular surfaces with dense fibrous tissue connecting the ilium and the sacrum. SI joints typically only have a few degrees of motion.

Diagnosing sacroiliac (SI) joint pathology can be challenging. One of the difficulties providers can run into in the evaluation of SI joint injury is in distinguishing between lower lumbar pain (lumbago) from SI joint pain. Specialized tests can be instrumental in making this distinction. It is vital to keep SI joint pain as part of the differential diagnosis of low back pain, with up to 30% of low back pain secondary to the SI joint. Pregnant women experience joint laxity due to hormonal changes, and this is when the SI joint is the most vulnerable to injury. Between the ages 40 and 50, the SI joint fuses decreasing the SI joints’ laxity. Fusion and or pregnancy may lead to hypermobility or hypomobility, which may exacerbate SI joint pain. Osteoarthritis is a common cause of SI joint pain.

However, there are multiple etiologies and a variety of factors that can contribute to SI joint injury. The overlap in symptoms with various causes of low back pain, as well as the numerous origins of SI joint dysfunction, make it not only a tough diagnose to make but also challenging to treat. SI joint injury can be acute but becomes chronic after three months of persistent pain. Chronic SI joint pain occurs when the free nerve endings within the SI joint degenerate or become chronically activated. Pain can be constant or intermittent for SI joint injury. Given the prevalence of mechanical back pain, it is essential to rule out or exclude a lumbar origin of suspected SI joint pain before diagnosis. It is often hard to pinpoint in which cases SI joint dysfunction is the primary reason behind a patient’s back pain. Some exceptions include trauma and pregnancy.

Extra joint mobility of the joint can result in pain in SI joint injury. However, hypomobility is a hallmark of ankylosing spondylitis, a common cause of inflammatory sacroiliac injury. SI joint dysfunction often occurs in unison with mechanical back pain. The sacroiliac joint may also be the site of pain referred from the lumbar vertebra rather than the origin of the patient’s pain. For example, degenerative disc disease at the L5-S1 vertebrae may become interpreted at the SI joint, but the source is much higher in the lumbar spine. There are multiple patterns of referral of pain for patients with SI joint injury. Including, the posterior thigh, knee, or foot. The most common site of pain referral is the posterior thigh, seen in 50% of patients. Complicating SI joint injury management further is a lack of clearly defined guidelines in the diagnosis and management of SI joint pain. MRI is the test of choice in the evaluation of SI joint dysfunction. Furthermore, radiographic-guided anesthetic injection provides a reliable way of determining SI joint pain in many cases.

The sacroiliac joint is a commonly targeted area of treatment of chronic low back pain as well. Conservative treatment options for SI joint injury often include physical therapy, home exercises, over the counter pain medication such as NSAIDs or acetaminophen. When conservative management fails, corticosteroid injections and radiofrequency ablative therapies are viable treatment options. In severe, refractory cases, surgery can fuse the SI joint. Patient education is essential in SI joint injury, including posture, proper lifting technique, stretching, and regular exercise. Weight loss helps SI joint pain, as well.