The sacroiliac joint. It’s an odd sounding name, but rest assured, it is real, it is a joint, and it can be source of low back pain, and even pain in the lower extremity. The name comes from the bones that form it. As we all know, a joint is formed where two (or more) bones meet, and it is often named for those bones. In the case of the sacroiliac joint, it is formed by the meeting of the sacrum (base of the spine) and the ilium (one of the bones of the pelvis).
It is a very strong and stable joint. The surfaces of the bones are irregular, allowing them to interlock to some degree. Between the bones is the synovium, a connective tissue the adds further strength. At the front and back of the joint are very strong ligaments that again make the joint stronger and more stable. Thankfully, it is very strong, because it puts up with a lot. Walking, running, going up and down stairs, jumping, sports activities and falls all can transmit an impact force up the lower extremity, across the sacroiliac joint and up the spine. Each joint along this path dissipates the force to some degree, but significant forces still have to cross the sacroiliac joint, and it stands up to them quite well.
The joint does move, but very little. There can be an up and down movement between the two bones, and there can be a little rotation at the joint. This movement has been researched extensively, and while there is some disagreement on the amount of movement and rotation, it is generally thought the amount of movement up and down is in the neighborhood of a few millimeters (a fraction of an inch) and perhaps two degrees of rotation, give or take a little. Weight bearing also helps to push the two bones together, adding further strength. A good paper describing the anatomy and function of the sacroiliac joint can be found at http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7580.2012.01564.x/full. Consider yourself warned however, it is long and technical, but is well researched and a good resource for those interested in this topic.
While it is strong, it can also be a source of pain, whether due to injury, wear and tear, or even due to pregnancy. The problem basically comes from excessive movement, either the up and down movement, or the rotational movement. Injuries may include falls or motor vehicle accidents. Wear and tear, is well, wear and tear. A lifetime of hard physical work, repetitive stresses from sports or other activities might be a cause, among many others. The laxity (loosening) of the ligaments that occur in pregnancy might also lead to excessive movement of the joint. Pain associated with sacroiliac joint problems is typically located in the lower back and/or buttock, left or right but not usually both. You can have pain in the lower extremity, usually not below the knee, but it is possible to experience pain in the lower leg and foot according to some studies. You might even have groin pain or pain within the pelvis itself. The abstract of an interesting study of location of pain can be read here: http://www.sciencedirect.com/science/article/pii/S0003999300900807. I’m not sure I would want to be a test subject in a study like this!
So, it’s a strong joint, it doesn’t move much and it can cause pain. What’s the big deal? The problem for those of us that treat back pain is actually determining what is the source of pain. As we said above, the pain from the sacroiliac joint is usually located in the lower back, buttock or thigh, and may go down as far as the foot. This same pattern may arise from the lumbar spine as well. Notice I’m only saying lumbar spine, because within that area are a number of structures that could give rise to the very same pain. So, we have to differentiate between the lower back and the sacroiliac joint. You certainly wouldn’t want to direct your treatment at the sacroiliac joint, when it is the lumbar spine causing the problem, or vice versa.
Well, c’mon, it can’t be that hard, can it? In a word, yes. It can be that hard. Old habits die hard in health care, and old habits as they relate to assessment of the sacroiliac joint are a real problem. Maybe your practitioner pokes certain spots on your pelvis and says they aren’t even, looks to see if your pelvis is level, looks at your leg length, has you bend to see if your pelvis moves in some fashion, asks you to bend forward and wonders if your pain is there as you return to upright standing. Each of these relates to an old testing procedure, that in one way or another, through good research, has been shown to be unreliable. I cringe every time someone comes in my office with back or lower extremity pain, and tells me that so and so told them they have one leg shorter than the other, and that means their sacroiliac joint is “out”. There have been a number of methods taught to measure leg lengths. Back in the dark ages, when I went to school, we were told to lie the person on their back, tug their legs out straight and then compare the location of those little bumps at the inside of the ankle, and just like that you can assess leg length. Or, if you wanted to be even more accurate, while lying flat, you measure from the point of bone at the front of your pelvis (anterior superior iliac spine for you anatomy lovers), to the bump at the inside, or outside, of the ankle with a tape measure, and compare left to right. It sounded good then, and it sounds good now, but it’s not accurate. Studies show it’s not reliable, and the reliability when comparing the results of measurements between multiple examiners doesn’t hold up. When the amount of movement is millimeters, and amount of rotation is around two degrees, you better be accurate. You can read an extensive review of leg length measurement techniques here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2628227/. So, what we thought we were measuring may not have been actual measurements, may not have had a correlation to the problem our patient was experiencing, or just may not have told us anything like we thought it did.
Beyond that, how do we know that if you have a short leg that it actually means anything about the state of your sacroiliac joint and whether it is the cause of your pain? Maybe you just have one leg a little longer or shorter than the other, you have all your life, and it has nothing to do with your pain.
So, the long and short of it is that all those techniques for evaluating the sacroiliac joint don’t tell us much. Now what?
Well actually, life got simpler. That’s a surprise, isn’t it. A fellow named Laslett studied the sacroiliac, and pretty much figured it out. He published a paper years ago that demonstrated a series of “provocation” tests could be used to assess the sacroiliac joint with significant accuracy. (The abstract is here: http://journals.lww.com/spinejournal/Abstract/1994/05310/The_Reliability_of_Selected_Pain_Provocation_Tests.9.aspx.) He went on to suggest that a McKenzie lumbar evaluation, combined with the provocation tests, made sacroiliac evaluation even more accurate, and published his findings (you can find the abstract here: http://www.sciencedirect.com/science/article/pii/S0004951414601252.) Provocation testing is simple. You stress the joint by pushing or pulling or twisting, simply applying a specific force to it, and look for a response. Add the McKenzie evaluation first, and you can, with accuracy, rule out the lumbar spine as the source of the pain, and then turn your attention to the sacroiliac joint if provocation testing is positive. It’s simple, and it works.
So there you have it! (I hope I haven’t lost you.) It’s not okay to be told you have a short leg, or a long leg, or your pelvis is not even, or your hips are “out” and all the rest of the things you hear from us health care folks. It is okay to have your back evaluated, then have some simple provocation tests performed, to know with reasonable accuracy that your low back, buttock or lower extremity pain is coming from your sacroiliac joint or your lower back. Treatment is generally just as simple. We can usually teach you some simple stretches that will take care of the pain, and get you up and going again.
Find a McKenzie certified or diplomed, you can find one using the therapist locator at www.mckenziemdt.org. Your pain may be from the sacroiliac joint, it might be from the lower back. You deserve to have these areas properly evaluated, using techniques that have some evidence behind them (evidence based medicine – that’s going to be a great topic for another post), to determine where your pain is coming from, and how it can be best treated.