The sacroiliac or SI joint is the articulation between the bone at the base of the spine called the sacrum and the bones on both sides of the pelvis called the ilium. Refer to the picture below.
Over 22 years of physical therapy, I have treated many patients with low back and buttock pain who were diagnosed with an SI joint dysfunction. The difficulty with diagnosing an SI joint dysfunction is that the SI joint has no specific distribution pattern of pain. Pain directly over the SI joint does not necessarily mean that the joint itself is involved. SI joint pain can very often be referred pain from other structures such as the disc, nerve root, or facet joints of the lumbar spine. Many physical therapists or physicians attempt to diagnose an SI joint dysfunction through palpation of bony landmarks as well as assessment of SI joint mobility. There is only a very small amount of motion in the SI joint i.e. 2-3 mm or 2-3° of gliding or rotation thereby making an accurate diagnosis very difficult. In addition, evidence based research refutes the reliability and validity of accurately assessing bony landmarks and SI joint mobility. McGrath et al has published an article, entitled “Palpation of the sacroiliac joint: an anatomical and sensory challenge” in which the concept of SI joint palpation is scrutinized. Freburger and Riddle performed a literature review looking at our ability to perform SI joint motion testing. They found poor inter-tester reliability, low sensitivity, and low specificity in several commonly performed tests. Inter-rater reliability is essentially the ability for multiple practitioners to come to the same diagnostic conclusion. If you have multiple individuals perform the same test, the results should be the same. Riddle and Freburger in another study noted that the ability to detect positional faults of the SI joint also has poor reliability. At present, the only acceptable method of confirming or excluding a diagnosis of a symptomatic SI joint is a fluoroscope guided intra-articular anesthetic block ie an injection directly into the SI joint. (Laslett et al) So how can I, as your physical therapist, assist in the diagnosis of an SI joint dysfunction? The answer: SI joint provocation tests!
Two recent studies by Laslett et al and Van der Wurff et al have demonstrated that there isn’t just one key or ideal SI joint provocation test. However, by performing several tests together, you can increase your sensitivity and specificity of detecting an SI joint dysfunction. Both studies reported that the accuracy of detecting SI joint dysfunction is increased if least 3 of the 5 tests are positive. Furthermore, if all 5 tests are negative, you can likely look at structures other that the SI joint. Van der Wurff et al reported that if at least 3/5 of these tests were positive, there was 85% sensitivity and 79% specificity for detecting the SI joint as the source of pain. Interestingly, another study by Kokmeyer et al agreed with the previous findings, but also noted that the thigh trust test alone was almost as good at detecting SI joint dysfunction as the entire series performed together.
Combining the two studies, there are 5 provocation tests to perform when attempting to diagnose SI joint pain:
- Thigh thrust/Femoral Shear test
- SI Distraction Test
- SI Compression Test
- Gaenslen’s Test
- FABER / Patrick’s test
The following video will demonstrate these tests. I would like to thank Mike Reinold, PT for his blog information that was used to complete this explanation of SI Joint dysfunction. Check out the video below!!
CORRECTION: I would like to clarify the SI distraction test as described in Laslett. I believe that he considers the direct posterior shear of the innominates as a distractive force of the ilium away from the sacrum. I initially interpreted this test as a compression of the SI joint via a distraction of the ASIS’s. I guess it depends on HOW you apply the force to the ASIS’s. Also, the sidelying “compression” test needs to be performed in a straight, linear fashion as well in order to compress the SI joint. It is important to place a towel roll under the lumbar spine in women in order to prevent sidebending stress t the lumbar spine. In OMT, we use the sidelying position to “distract” the SI joint using more of a rotational force on the lateral edge of the ilium in order to “open up” and distract the SI to get a feel for joint play. As you can see, these tests are not definitive for exactly HOW they stress the joint but they are specific for a stressing maneuver TO the SI joint.