This week’s post is the third and final installment of the Sacroiliac Joint (SIJ) Pain Series. I hope you’ve enjoyed learning about this specialty topic. If you’ve just recently joined our SIJ conversation, I encourage you to check out part 1 and part 2 where I discussed the following:
Today I’ll be explaining the Lateral Sub-System (LSS), it’s role in SIJ stability, and how dysfunction in this system contributes to SIJ symptoms. Let’s get started! The LSS plays an integral part of coordinating walking and running type activities. Are you sensing the pattern here with the SIJ and its three muscular systems being related to gait mechanics?! The LSS is responsible for allowing us to stand on one leg, which is critical for being able to swing our opposite leg forward during single leg stance activities (1-4). It’s also a major player in our ability to balance (1-4). In other words…it’s kind of a big deal. So which muscles are part of the LSS specifically? The gluteus medius, tensor fascia latae, adductor group, and quadratus lumborum.
Notice here that the LSS works in a cross pattern, just like the POS. Using the diagram above, the left quadratum lumborum pairs with the right qluteus medius, right tensor fascia latae, and the right adductor group. This system coordinates together to keep the body standing tall over the right leg by stabilizing the pelvis to maintain a relatively level position to the ground below, which simultaneously creates a stability force throughout the right SIJ. When the pelvis stays parallel to the ground in this way, the body is then able to efficiently swing the opposite leg forward with little effort. However, when there is an issue within this system, balance and single leg stance activities become significantly challenged and the SIJ becomes compressed, resulting in what’s called a trendelenburg sign (1, 2). When this happens, the left hip will drop as the left leg attempts to swing forward, creating a side bending motion of the torso to the right to counterbalance the left hip dropping. Over time, this compensatory pattern creates right sided low back pain and significantly increases our risk for falling (1-4).
When there is an issue within the LSS, it’s often due to a gluteus medius or adductor weakness, and the low back and SIJ attempt to compensate for this dysfunction. Thus, in order to re-educate the LSS system, gluteus medius and/or adductor strengthening are often part of the rehab process. Some examples of exercises that you can incorporate prophylactically into your strength training routines to help keep the LSS strong can be found here in video one and video two.
After reading the entirety of this SIJ Pain Series, I hope you have a better understanding of what the SIJ is and how the three muscular sling systems (POS, DLS, and LSS) work together to help our bodies move efficiently during our walking and running activities. If you have questions about anything I covered here, please don’t hesitate to reach out. I’d be happy to speak further with you. More importantly, if you suspect you may have SIJ dysfunction and are local to Santa Barbara, set up an appointment with me so I can help you uncover the root of the problem and guide the proper exercise prescription and get you back to moving pain free. Not local? No problem! I’d be happy to help you find a physical therapist near you! Let me know where you live, and I’ll reach out to my PT network to find a therapist who can work with you.