Does the sacroiliac joint move a little or a lot? Experts generally agree that, in spite of being one of the most stable joints in the body, the sacroiliac joint (SIJ) does have at least a little movement in normal activities. There is much less agreement, though, about how much movement is good, with published descriptions of “normal” (asymptomatic) SIJ motion ranging from 1 to 8 millimeters of glide and from 1 to 18 degrees of rotation.1
And does the amount of SIJ movement relate to pain? And if it does, is more or less movement better? There is also very little agreement about these questions, with one study citing up to 30 degrees of non-painful SIJ rotation (in warmed-up gymnasts), while another study found almost no SIJ movement in subjects with SI pain.2
Conventional wisdom says the painful SIJ is most often on the more mobile side. Thus, improving the stiffer side’s mobility could redistribute the movement load more evenly and help relieve the “hypermobility” or “laxness” of the painful side.
In my own manual therapy practice, this approach seems to help many clients, though others (including, occasionally, myself) seem to benefit more from the opposite approach (working on the already-more-mobile side). These exceptions to biomechanical predictability suggest there are probably many factors involved in SI pain (for example, joint hydration, proprioception, pain perception phenomena, etc.) beyond movement laxity or stiffness.
Given these considerations, in our Advanced Myofascial Techniques seminars and training videos, our current working hypotheses (supported by both our practice observations and others’ formal research3) are that:
• The amount of SIJ movement does not seem to correlate very well with clients’ pain (people with pain can have either very mobile or very immobile SIJs). However,
• Pain does seem more common in those with large differences between left and right SIJ mobility; and,
• Strategically, when there is a difference in stiffness between the two SIJs, inviting more movement on the less-mobile side is an effective way to begin addressing SI and related pain, with the consideration that,
• If pain does not improve after working the less-mobile side, the complementary approach (working with the more-mobile side with an aim to increase nonpainful proprioception, joint hydration, etc.) is the logical next step, as this can often relieve pain when the opposite approach doesn’t.
The SIJ’s balance of stiffness and mobility can be affected by a great many soft-tissue structures, most obviously the numerous SI ligaments (the strongest in the body) arrayed around the SIJ (Image 1); and by the many myofascial structures that cross the SIJ (the piriformis, gluteus maximus, and sacral multifidus muscles; the thoracolumbar fascia, etc.). For simplicity, I’ll describe just one technique here, and focus on one of the many structures that can influence sacral mobility.

The Interosseous SI Ligament Technique
The interosseous SI ligament (Image 3) is the primary structure that restrains gapping of the SIJ; it is also tensioned by posterior glide of the ilium against the sacrum (Image 5). Its short fibers are just behind the SIJ capsule, deep to the posterior SI ligaments (Images 3, 5). Although there is some disagreement about the role these ligaments have in pelvic pain (one argument being that because they are so strong, they are unlikely to be strained or sprained), these dorsal structures are the most richly innervated of the sacral ligaments, and have many sensory nerves and mechanoreceptors.4 Their rich innervation may help explain why studies show that the SIJ can be the main source of nociception (pain-triggering signals) in 14–22 percent of all low-back pain.5

Our technique for working with the interosseous SI ligaments borrows its inspiration from a common orthopedic test—the SI distraction or “squish” test. Although there is some controversy about this test’s objective inter-rater reliability (as there is with most movement-palpation tests), we employ it not so much as an objective test, but instead as one technique for increasing evenness of left/right joint mobility, and (especially) increasing our clients’ subjective proprioception through the technique’s novel sensation and focused attention. These two goals (more options for movement and refined proprioception) often result in less pain (which itself is a subjective rather than objective phenomenon). As you practice this simple but effective technique for working with SI pain (using the instructions and considerations outlined in the Key Points sidebar), keep these two goals in mind.

Key Points: Interosseous Sacroiliac Ligament Technique

Indications
• Sacroiliac joint (SIJ) pain or irritation.
• Low-back pain—14–22 percent of low-back pain seems directly related to sacroiliac (SI) issues.
• Sciatic pain (buttock and/or posterior leg pain), since the sciatic nerve passes just anterior to the SIJ; and piriformis, etc., can be SI ligament synergists.

Purpose
• Increase nonpainful proprioception.
• Balance left/right SIJ mobility.
• Improve intra-articular hydration of the SIJs.

Instructions
• Beginning with a very light touch (no more than 10 grams of pressure at first) over the anterior superior iliac spine, compare the perceived posterior mobility (resilience or stiffness) of the left and right ilia (Images 2, 4, 6).  
• Ask proprioceptive questions such as “What difference do you feel, left to right?” Or, “I feel this side move more, this side move less. What do you feel?” Help the client distinguish any pain (often, but not always, on the more mobile side) from the sensations of stiffness.
• If 10 grams of pressure does not cause pain, gradually increase pressure, continuing to ask for the client’s proprioceptive report.
• Press with one hand, while the other hand stabilizes the client’s pelvis, so as to isolate posterior movement of the ilium at the sacrum, rather than rock the entire pelvis from side to side.
• Vary the angle of your pressure slightly, feeling for outward, upward, and inward mobility of one innominate against the sacrum, monitoring for movement restrictions, sensitivity, or relief from pain.
• If pressure relieves pain, wait with sustained pressure for several breaths, encouraging the client’s relaxation and refined proprioception.

For More Learning
• “Pelvis, Hip & Sacrum” or “Advanced Ilia and SI Joints” in the Advanced Myofascial Techniques series of workshops and video courses.
• Advanced Myofascial Techniques, Volume 1, Chapter 13 “The Sacroiliac Joints” and Chapter 14 “The Ilia” (Handspring Publishing, 2015).

Notes
1. H. M. Buyruk et al., “Measurements of Sacroiliac Joint Stiffness with Colour Doppler Imaging: A Study on Healthy Subjects,” European Journal of Radiology 21, no. 2 (December 1995): 117–21; Diane Lee, The Pelvic Girdle: An Integration of Clinical Expertise and Research, 4th ed. (Edinburgh: Churchill Livingstone, 2011): 61–2.
2. G. L. Smidt, "Innominate Range of Motion," A. Vleeming et al (eds.) Movement Stability and Low Back Pain: The Essential Role of the Pelvis (Edinburgh: Churchill Livingstone, 1997): 187–1911; T. J. Kibsgård et al., “Radiosteriometric Analysis of Movement in the Sacroiliac Joint During a Single-Leg Stance in Patients with Long-Lasting Pelvic Girdle Pain,” Clinical Biomechanics 29, no. 4 (April 2014): 406–11.
3. L. Damen et al., “The Prognostic Value of Asymmetric Laxity of the Sacroiliac Joints in Pregnancy-Related Pelvic Pain,” Spine 27, no. 24 (December 2002): 2,820–4.
4. K. R. Grob, W. L. Neuhuber, and R. O. Kissling, “Innervation of the Sacroiliac Joint of the Human,” Zeitschrift für Rheumatologie 54, no. 2 (March–April 1995): 117–22.
5. D. W. Polly and Daniel Cher, “Ignoring the Sacroiliac Joint in Chronic Low Back Pain is Costly,” ClinicoEconomics and Outcomes Research 8 (2016): 23–31.

Til Luchau is a Certified Advanced Rolfer, the author of Advanced Myofascial Techniques (Handspring Publishing, 2016), and a member of the Advanced-Trainings.com faculty, which offers distance learning and
in-person seminars throughout the United States and abroad. Contact him at info@advanced-trainings.com and Advanced-Trainings.com’s Facebook page.