The Sacroiliac (SI) joint is the joint between the sacrum (the lowest portion of the spinal column) and the wing bone of the pelvis called the ilium. Everyone has a left and a right SI joint. The bony pelvis is made up of three bones; the sacrum, the left ilium and the right ilium. The SI joint moves a small amount (2 to 4 degrees) and transfers heavy loads from the legs to the body and from the body to the legs. The SI joint (like other joints in the body) can be damaged or can function improperly. In these cases, the SI joint can be a source of pain.
Evaluation of patients with suspected SI joint problems consists of; a patient history, a physical examination including a series of stress tests (provocative testing) of the SI joint, and if necessary a diagnostic injection of the SI joint.
The patient history is a series of questions asked by the health care professional of the patient. These questions are designed to paint a picture and tell a story about the patient’s pain. When did the pain start? How did the pain start? What makes it better? What makes it worse? The history helps the health care professional differentiate SI joint pain from pain coming from other sources.
The physical examination is the second part of the diagnostic workup. The examination typically includes inspection (looking at the patient’s body during sitting, walking, or other activities), palpation (the health care professional (HCP) touches or presses on various anatomic structures to see if they are tender or painful), range of motion testing (checking the various joints such as the spine and hips to see if they move normally), neurologic examination (testing the patient’s strength, sensation, and reflexes) and other tests. Physical examination of the patient with presumed SI joint pain includes careful examination of the lumbar spine, the SI joint and the hip/pelvic area.
The physical examination of the sacroiliac joint includes a series of tests performed by the HCP that stress the SI joint. These tests (referred to as the provocative tests) apply stress to the SI joint in different directions. These tests are referred to as provocative tests because they are designed to provoke or produce a pain response in a damaged or painful SI joint. Studies have shown that multiple positive findings (three) of a series of (five) specific provocative tests can be quite helpful in making the diagnosis of SI joint dysfunction. A positive test is one where pain that is similar in nature and location to the patient’s typical day to day pain is caused or “provoked” by stressing the SI joint.
Several clinical studies have evaluated the effectiveness of the provocative tests in making the diagnosis of SI joint pain.1,2 Mark Laslett, a physical therapist (PT) working in clinical research, published an important article on this topic in 2008. In his study, he examined the usefulness of the series of provocative tests to help make the diagnosis of SI joint dysfunction. When 3 of 5 of the tests produce pain at the SI joint, the provocative tests have 91% sensitivity. Sensitivity means the provocative testing (3 of 5 tests positive) is positive when the patient actually has pain coming from the SI joint. When less than 3 of 5 of the provocative tests are positive the testing has 78% specificity. Specificity means that the provocative testing is negative when the patient does not have SI pain. Specificity and sensitivity are then used to calculate the predictive value of the provocative tests.
The provocative tests are typically performed during the physical examination. These tests are a small but important part of the complete patient evaluation. The tests are performed with the patient lying either on their back or on their side on the examination table. The examiner applies a gradually increasing force to the bones of the pelvis or femur (thigh bone) in order to stress the sacroiliac joint. If the patient reports pain that is similar to their typical day to day pain, the test is considered positive. For convenience to the patient and to the examiner, the tests are typically performed in the following order.
The first test performed is called the Distraction test. The patient is lying on their back. A pillow is placed under their knees. The examiner leans over the patient and places their hands on the front of the patient’s bony pelvis (the left and right ASIS, anterior superior iliac spine). The examiner then applies a gentle and gradually increasing force in an outward and downward direction on these bones.
The second test is called the Thigh Thrust test. The patient continues to lie on their back. The examiner brings the patient’s leg on the painful side up until it is at a 90 degree angle with the knee relaxed. The examiner then applies a gentle and increasing force through the patient’s thigh bone in a direction straight down towards the table.
The third test is called the FABER test. FABER is short for flexion, abduction, external rotation. This is the direction that the hip is positioned during the test. The patient remains positioned on their back. The examiner moves the leg of the painful side into a 90 degree angle, rotates it outward, and then places the foot of that leg over the opposite leg positioning it just above the knee. The examiner then applies a gentle force in a downward (toward the table) direction to the involved side knee. This test is positive if the test reproduces the patient’s typical pain in the posterior buttock area. Some patients may have pain reproduced in the groin or anterior (front) hip area during this maneuver. Anterior pain is more indicative of hip problems. Posterior pain is more indicative of an SI joint problem.
The fourth test is called the Compression test. For this test, the patient rolls on to their non-painful side (painful side up). The patient’s hips and knees are slightly flexed. A pillow is placed between the patient’s knees. The examiner positions their hands, one on top of the other, in the soft spot between the greater trochanter (lateral bony point of hip) and the top of the iliac crest (pelvic bone). A gentle, gradually increasing force in a downward direction is then applied.
The fifth test is called Gaenslen’s test. The patient is again positioned on their back. The painful side leg is positioned so that it may be extended downward off the side of the table. The non-painful leg is flexed towards the patient’s chest. The patient holds the flexed side knee. This maneuver stabilizes the opposite side of the pelvis. The examiner then gently places the painful side leg off the edge of the table. The examiner applies a gentle force in a downward direction to the front of the painful side thigh near the knee. Similar to the FABER test, reproduction of posterior buttock pain is indicative of a positive test. Pain reproduced in the anterior (front) hip may indicate problems with the hip.
Complete physical examination will also include careful examination of the lumbar spine and hip. As mentioned before, pain coming from the lumbar spine or hip may present in a manner that is similar to pain coming from the sacroiliac joint. If examination of the lumbar spine and hip are negative and if three of five provocative tests are positive, it is likely that the patient has problems coming from the SI joint. Typically, positive provocative testing would provide a strong enough diagnosis to proceed with non-surgical treatments of the SI joint such as a physical therapy program and/or a trial of SI joint belting.
If these initial non-surgical treatments are unsuccessful, then the diagnosis is typically confirmed with a diagnostic injection of the sacroiliac joint. This is a procedure where numbing medication such as lidocaine is injected into the joint under fluoroscopy (live x-ray). If the pain from the SI joint is temporarily relieved with injection of the numbing medicine, this is a positive or confirmatory injection. More invasive, non-surgical treatments such as SI joint steroid injection or SI joint radiofrequency ablation (RFA) may be performed if the diagnostic block is positive. If non-surgical treatments do not provide a long term solution for the pain and altered function coming from the SI joint, minimally invasive sacroiliac joint fusion may be an option.
- Laslett M. Evidence Based Diagnosis and treatment of the painful Sacroiliac Joint. J Man Manip Ther. 2008;16(3):142-52.
- Szadek KM, van der Wurff P, van Tulder MW, Zuurmond WW, Perez RS. Diagnostic Criteria for Sacroiliac Pain, A Systemic Review. J Pain. 2009;Apr:10(4):354-68.