Jackson and Porter bring up the fact that there is essentially no research on the topic of non-painful SIJ Dysfunction. Once again, just because there is no research in an area, does not indicate that it should be dismissed as non-existent. We tend to become overly reliant on our pain provocation tests. So what do we do? We definitely recommend still utilizing your clusters, palpating soft tissue, and utilizing subjective information such as Fortin's Sign to aid in diagnosing painful SIJ Dysfunction. As for non-painful dysfunction, practice and implement the motion restriction tests that you are taught in school. We are trained to be competent in tests like Lachman's and Drawer Tests that require identification of differences in movement around a few millimeters. In theory, we should be able to identify some abnormalities in the sacroiliac joint as well. Now, we recognize that research has shown poor reliability for those tests and for good reason, but they may still aide in picking up severe restrictions that will lead to diagnosis and treatment in order to facilitate the return to normal mobility.
Jackson R and Porter K. The Pelvis and Sacroiliac Joint: Physical Therapy Patient Management Utilizing Current Evidence. Current Concepts of Orthopaedic Physical Therapy, 3rd Ed. La Crosse, WI. 2011.