The Sacroiliac Joint: Dysfunction and Discovery, Part One.

The Sacroiliac joint is the point in your back where the base of the spinal column (known as the sacrum) meets the pelvis-and leads onto the tailbone. If you place your hands on your lower back right now, you will feel two bony ‘bumps’ either side of your lower back which are, if feel outwards, in-line with the ridges of your hips.  These bumps are the top of your sacroiliac joint. Sacroiliac joint (SIJ) pain is an under-appreciated source of mechanical low back pain, affecting one third of individuals with chronic, non-radicular pain (Cohen 2013). Quite often, it affects perfectly strong, fit people who have never had back pain before. It can be a baffling, painful experience for the sufferer and may go misdiagnosed. In the first of our series on the SIJ, we look at the history of this unique joint and how it has evolved with us. We will then highlight what it does, what can go wrong and the symptoms of SIJ pain. Finally we will look at what can be done to relieve the pain from this increasingly common back complaint.

A brief history of time

Bipedal movement in hominids started-with some debate-around four to seven million years ago. The reason for this is also debated, but the commonly identified reasons include travel (particularly over rivers, carrying young etc), reaching food, avoiding predators and procreation.

With the transition from quadrapedal to bipedal gait we saw an evolution in the homonid anatomy. The shoulder girdle become more unstable, lower-limb length increased and the anatomy of the hips and sacroiliac joint also changed from a relatively mobile to a more rigid structure-as it was required as a fulcrum to control lumbo-pelvic stability and maintain our centre of gravity over our base of support during walking. To allow fluent walking in humans, the hips flared outward in the sagittal plane to provide a more optimal lateral attachment site for the gluteus medius muscle. Also, a dramatically increased attachment site for the gluteus maximus muscle has changed this muscle-a relatively minor muscle in the short legged chimpanzee-into one of the largest (and the strongest) muscle of the human body (Lovejoy, 1988, 2007). The ligaments of the sacroiliac joint also became much more robust with upright walking (Vleeming et al 2012). In short, the increase in gluteal muscle strength and increased ligament connections meant the sacroiliac joint had, to all intents and purposes, been reinforced, welded tight and had a V12 inserted where there was once a 2 stroke engine…

During the mid-point of the last century, clinical opinion stipulated clearly that the SIJ was immobile and unlikely to be a source of lower back pain. This consensus continued and remained largely unchanged until about twenty years ago. It has in that time become increasingly accepted that the SIJ was capable of being both mobile and immobile (a characteristic distinctly unique to the SIJ). It is now understood that too much or too little movement in the SIJ causes pain. To explain movement in the SIJ, lie on your back and place your hands under your lower back. Then flatten your lower back onto your hands, then arch your back the other way. This anterior, posterior tilt is the principle movement of the SIJ and you will further see the importance of this movement in part three when we discuss the SIJ and hip pain.

With normal function, this forward and backward movement involves a fine balance between the muscles of the SIJ and the approximation of the joint surfaces and their ligaments described above. Too much or too little movement (or too much on one side and too little on the other) can lead to increased sagittal torque and stress to the SIJ. A good way to visualize this stress is to take a dishcloth and wring it out. The opposing, rotational forces create tension in the centre of the dishcloth and this tension pushes water out. In the SIJ this imbalanced tension causes friction, inflammation and pain.  

So these problems can be caused by muscle imbalances in the gluteal region, hamstrings, core and back. Other reasons for this can include sleeping positions (people who sleep in the recovery position are more likely to get SIJ pain). Women after pregnancy are also prone to SIJ pain, due to excessive release of-the fittingly named-ligament relaxing hormone, relaxin.

The symptoms of SIJ pain can include.

• Pain in one side of the back. From the Lower back into the outer hip and groin. Pain is usually ‘dull’ and annoying but rarely moves down the leg or up the body.
• Pain that is worse in the morning, but gets better as the day goes on.
• Pain that is notably worse with sitting but can be aggravated by certain activities such as running-or any activity that involves running or high-intensity bipedal movement. Pain can also increase going from sitting to standing, but goes away once standing upright.
• SIJ pain is likely linked to one leg being longer than the other (this can also be the cause of the muscles being imbalanced).

Our next publication will look a little more at how to manage SIJ pain. We will finally, in part  three, look at the link between SIJ and hip pain.

If you are suffering from SIJ pain, or would like to know more about SIJ pain contact us today by clicking the ‘book now’ tab at the top of the page. You can also contact me directly, paul@moldphysiotherapy.co.nz.

Thanks for your time and see you at our next blog!