Welcome back to the second installment of Sacroiliac Joint (SIJ) dysfunction. In last week’s post I introduced what the SIJ is and why it’s a commonly associated with low back pain complaints. I also explained that there are three important muscular systems that influence the SIJ, and went into depth about the contributions of the Posterior Oblique System (POS). This week, I’m going to explain the Deep Longitudinal System (DLS) and it’s contributions to SIJ stability.
The DLS is made up of the following components (1):
This system is especially important during walking and running activities as it plays a major role in stabilizing the SIJ and controlling the amount of healthy pelvic rotation that needs to occur with every step we take (1,2). As we heel strike with our right foot, the right bicep femoris muscle (one of the three hamstring muscles) is responsible for regulating forces between the lower leg and pelvis via the sacrotuberous ligament which acts as a stabilizing force for the right SIJ. These forces are then transmitted further up the chain through the thoracolumbar fascia and spinal erector muscles (multidifi and erector spinea group) to control rotation at the torso and assist with continued propulsion as walking/running continues (1, 2). If this DLS is not working optimally, then the right side of the pelvis ends up rotating too far forward as the foot strikes the ground, creating a compressive force on the right SIJ and lower back region, resulting in pain and discomfort. This is often due to inadequate hamstring strength, which is common with hamstring strain injuries, as well as, lateral ankle sprains. Wait, ankle sprains can influence this system too? Yes, limitations in ankle range of motion disrupt the transfer of forces through the bicep femoris muscle, which is a primary player in force regulation of the DLS. Thus, I always check the DLS with patients who have a history of ankle related injuries, especially those with low back pain complaints.
So how do we address DLS dysfunction? Often, treatment includes restoring adequate mobility to the hip and ankle joints, as well as focusing on hip extension exercises and ankle strengthening exercises for improved sequencing and loading through the DLS. However, in order to best understand what is contributing to your SIJ dysfunction, consult with you local physical therapist first 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.
Stay tuned for next week’s final installment of this special series on SIJ dysfunction. I’ll be explaining how the Lateral Sub-System contributes to SIJ stability – you won’t want to miss it!