The sacroiliac or SI joint, located in the low back on either side of the spine, is a common source of back pain. However, despite its role in spine-related problems, few patients are familiar with the SI joint.
Because sacroiliac joint pain can present with symptoms that resemble a variety of other spine and back problems, it is a source of confusion for many patients and a potential diagnostic challenge for orthopedic and sports medicine physicians.
What Is the Sacroiliac (SI) Joint?
The SI joint is located to the side of the spine, just above the tailbone (coccyx). It connects the sacrum (a bone of the low spine composed of fused vertebrae) and the ilium, or pelvic bone.
Unlike most joints of the body, the sacroiliac joint sees little movement. This diminutive joint is strong, thanks to the many ligaments that support it. Its purpose is to act as a shock absorber (of sorts) and a buffer between the upper and lower portions of the body.
The symptoms of sacroiliac joint problems strongly resemble other issues of the lower spine, including sciatica. Pain radiates from the low back into the buttock and thigh, typically with a stabbing sensation. Patients may feel the pain on both sides; however, many experience it only on one side.
Causes and Diagnosis of SI Joint Pain
SI joint pain can be the result of trauma or another medical condition. Falls (specifically on the buttocks), car accidents, heavy lifting and sports injuries are some of the potential traumatic causes.
Sacroiliac problems also can emerge during pregnancy or as the result of an infection. Obesity, scoliosis, arthritis and problems in adjacent structures of the back can all lead to pain in the sacroiliac joint. Finally, overuse and repetitive motion, in sports, work, etc., can result in a cumulative injury to the SI.
Diagnosing SI problems is exceptionally difficult. Because pain can be referred and resembles other conditions, the origin is difficult to determine. Likewise, imaging tests are rarely conclusive.
Some physical manipulation tests, known as sacroiliac provocation tests, can be helpful. However, the most effective way to confirm the diagnosis is with a joint block injection. In this procedure, the orthopedic or sports medicine physician injects a nerve block into the joint. If the pain subsides by at least 50 percent — and stays away for six weeks — the doctor may confirm the diagnosis.
Treating SI Joint Pain
Sacroiliac joint pain can be treated with a conservative approach, including nonsteroidal anti-inflammatory drugs (NSAIDs), physical therapy, postural or activity modifications or a supportive orthopedic belt. Periodic corticosteroid injections can help control pain.
Radiofrequency nerve ablation has been shown to be highly effective for chronic low back pain related to the sacroiliac joint.
Surgery for sacroiliac joint pain involves fusion of the joint, either arthroscopically or in an open procedure.
Some of the most effective, yet minimally invasive, treatment options involve orthobiologic (regenerative medicine) injections. Bone marrow-derived stem cells and platelet-rich plasma injections, performed with imagery guidance, are highly effective for treating this condition. With little risk of side effects, these treatment protocols are effective at reducing SI joint pain and restoring function in the long-term.