The Sacroiliac Joint (SIJ) has been identified as a potential source of low back pain, although usually not the most likely source of pain. So than how do we know when the SIJ is involved; well its tricky. Conservative diagnostic (Dx) tests to rule in or rule out true SIJ pathology have been a source of confusion. However Dr. Andrew Tomas just wrote up a great article to provide some clarity into the confusing Dx of the SIJ. Here is a summary of the paper (from Orthopedic PT Practice Vol 25, No 4. 2013)
SIJ can be Dx by:
1. movement tests such as Gillet and standing flexing test to assess correct position relative to the pelvis.
2. palpation of bony landmarks to evaluate the "correct" position and alignment.
Unfortunately, the reliability of these tests are at best as good as a flip of a coin. This is because SIJ motion is so small (2.5degr of rotation and 0.7mm of translation [and no differences in healthy and symptomatic patients]). And there's too much soft tissue (over 7 layers and 7cm from the skin) before you touch a small bony landmark. Additionally, the relevance is so low because of the similarity in + and - tests in healthy and unhealthy patients.
3. location of pain and subjective history.
More bad news, no aggravating or relieving factors have been identified as having any value in Dx SIJ pain. Fortin et al were able to map out a consistent area of pain from the SIJ that consists of pain that is inferior to the PSIS. However, Wurff et all found that the "fortin area" was in deed not consistent to Dx with. Bummer. So you cant use pain location to assist with any clinical prediction.
4. Finally we could use 'pain provocation special tests' that focus on generating stress to the SIJ. Individual special tests aren't that great on their own but when coupled with other similar special tests (clinical prediction rule?) we see more reliable findings. In fact, Laslett et al and Van Der Wurff et al found good sensitivity and specificity when 3 or more pain provocation special tests were positive.
SUCCESS! In fact, if you follow the model below, you'll see that just two tests that have the higher specificity (Sacral Distraction) and sensitivity (Thigh Thrust) can identity SIJ pathology. If both these tests are positive you have a 88% of being right and a 78% of not being wrong. If both tests are not positive than follow the algorithm to rule in or rule out.
