You’ve just finished crushing it this morning in the gym doing a combination of running and resistance training. You’re flying high on your exercise endorphins, and impressed with your new levels of fitness. Later on while sitting at your desk you start to notice an ache in your low back near the intersection of your spine and pelvis. First it’s just awareness…eh, that will probably sort itself out once I stand up and stretch…but then you notice it getting progressively worse over the course of your day. What the heck?! I probably just need to stretch. You spend some time foam rolling and stretching when you get home. It feels a little better but the discomfort is still there. The next morning, your low back feels tight and achy, especially when you bend forward or to the side, but seems to loosen up a bit as you get moving. You decide to not let this discomfort sideline you. You’ve got a track workout planned with a friend later that afternoon. While at the track, your pain is there but doesn’t keep you from participating, but later that evening the pain worsens and you’re you’re left wondering if it’s something more serious. Was it the stadium stairs or maybe the sprints that made it worse? You decide to take a few days off to rest and let your body recover. When you’re feeling better you resume your workouts only to immediately notice that same nagging pain in your low back and now it’s traveling into your hip. Ugh!
This is a common story I hear from my patients with low back pain, and it’s often related to Sacroiliac Joint (SIJ) dysfunction. The SIJ is where the spine (sacrum specifically) and pelvis come together. We all have two SIJs, one right and left. These joints are especially important for helping to distribute forces between the lower body and torso, and share many muscular and ligamentous attachments with the hip, pelvic floor and low back (1,2, 3). The SIJ is designed to provide increased stability to the pelvis while we’re in motion, which is especially important when we’re performing higher impact activities (1,2). When the body isn’t able to efficiently distribute these forces between the torso and lower body, the SIJ often becomes symptomatic. This can happen on one side or both, depending. The failure to effectively transfer these forces results in compressive loads being placed on the SIJ itself, resulting in pain and discomfort near the joint and/or referring symptoms to the surrounding low back and hip regions (1,2, 3).
How does this imbalance in force transfer occur? Great question. It depends, and in order to best understand the answer to this question, we first need to discuss the three muscular systems that play an important role in SIJ health: the Posterior Oblique System (POS), the Deep Longitudinal System (DLS), and the Lateral Sub-System (LSS) (1,2). These three systems are critically involved in the distribution of forces through the body, and due to their complexity, each deserves their own blog post. Therefore, this week I will speak about the POS, with the next two posts being dedicated to the DLS and LSS, respectively.
Let’s dive into the POS. This sling encompasses the latissimus dorsi on one side of the body with the opposite glut maximus (the blue shaded area in the image on the left) via their connector the thoracolumbar fascia (the white area in the picture between the muscles around the low back region). When describing this muscular sling, I often tell my patients to imagine they’re wearing a beauty pageant sash. The muscles and fascia that run along the backside of the sash make up the POS. Now take a look at where the SIJ is in relation to this system…see where the thoracolumbar fascia is? Now think about how our bodies move when we walk or run – our right arm swing is paired with our left leg swing. As we push off, the left glut max contracts and enables our propulsion forward. Simultaneously, the right latissimus dorsi is extending our arm back behind us. This pairing creates a counterbalance, enabling right rotation to happen at our torso, left rotation at our pelvis, and thus generating a healthy amount of tension throughout the thoracolumbar fascia to create a stability force through the left SIJ. Now if there is weakness in the muscles of this sling, or if the timing sequence of these muscles becomes altered, or if someone doesn’t have enough range of motion in their hip or torso to activate this muscular sling effectively, then the SIJ looses it’s sense of stability. When this happens, the forces that would have otherwise been absorbed by the thoracolumbar fascia are now being transferred directly to the SIJ, resulting in compressive loading forces that eventually generate pain and discomfort. These concentrated forces need to be redistributed throughout the POS in order to resolve pain and low back discomfort.
Now remember that song Dry Bones from your childhood? It’s the song that goes “Your thigh bone’s connected to your back bone and your back bone’s connected to your neck bone…” Well, they were right, and the song goes on to connect the neck bone to your head bone and so on. Case in point, our hips and shoulders absolutely impact each other and contribute to low back pain if one or both isn’t working optimally.
So maybe your nagging low back pain is really a SIJ dysfunction? And maybe your POS needs some assistance? What should you do? First, consult with you local physical therapist to properly evaluate and diagnose the root of your problem. Treating the symptoms without a good understanding of the root cause will only give you a temporary solution. If you’re looking for guidance on how to strengthen your POS prophylactically, follow this link for a series of helpful exercises you can start to incorporate into your workouts.
Now remember earlier when I said this would be a 3 part blog series? You might think your SIJ pain is from your POS, but it could also be from one of the other slings I haven’t yet explained: the Deep Longitudinal System or the Lateral System. Stay tuned for next week – SIJ Pain Part 2!