Quadratus Lumborum and Erector Spinae in Scoliosis -Why SI Joint Pain Keeps Returning

Dear reader,

One recent case at my clinic in Marylebone reminded me again that mild scoliosis is rarely just a simple side bend. It is usually a three dimensional story. The spine rotates. The ribs shift. The lumbar tissues start behaving differently from one side to the other. Then the pelvis joins the drama, and usually one poor area ends up paying the bill.

In this case, the left side was clearly doing too much.

The client came in with left sided pain around the sacroiliac region. That familiar ache sitting low near the back of the pelvis, the kind of pain that often becomes more noticeable with standing too long, walking unevenly, climbing stairs, or simply existing in a slightly irritated human body. On assessment, the pattern suggested that the left lumbar pelvic side had become the chief stabiliser of the whole structure.

This is where many people misunderstand these presentations. They think the painful side must simply be weak. Often it is the opposite. The painful side is the side that has been working overtime for months, sometimes years, trying to stop the whole system from collapsing into a less efficient pattern.

Here the likely overworkers were the left quadratus lumborum, the left erector spinae group, and parts of the left lumbopelvic complex. These tissues appeared to be bracing and gripping in response to the rotational pattern above and the uneven pelvic loading below. In plain English, the left side had become the loyal but exhausted employee who never gets a holiday.

When the trunk rotates and the pelvis does not share load evenly, the SI joint region can become irritated quite easily. Sometimes the SI joint itself is the main source of pain. Sometimes the pain is referred from nearby lumbar structures. Sometimes trigger points in quadratus lumborum or the gluteal tissues add their own opinion to the conversation. The body, sadly, is not always concise.

What matters clinically is that the pain is often not random. It usually follows logic.

With mild scoliosis, one side of the ribcage may sit differently, one lumbar side may become more prominent, and the pelvis may develop a subtle obliquity or torsion pattern. Even a functional leg length difference can begin to appear as part of the compensation. Then the hip starts moving with slightly altered mechanics, gait becomes less symmetrical, and the lower back and pelvic muscles keep tightening to maintain stability. The result is not just tension. It is organised compensation.

This is exactly why I do not like reducing these cases to a single sore spot.

If somebody only chases the pain at the left SI joint, they may miss the wider chain that keeps feeding it. At JANMI, I look at how the foot, knee, hip, pelvis, ribcage and scapular relationship may be influencing that one painful point. A rotated trunk can change rib mechanics. Altered rib mechanics can influence spinal tone. That changes lumbar loading. Then the pelvis loses its calm, the hip loses its rhythm, and the glutes and QL begin acting like emergency ropes holding a tent in bad weather.

The aim in this kind of case is not to bully the body into perfect straightness. That is rarely the right obsession. The aim is to reduce asymmetrical load, calm the tissues that are overgripping, improve how the system shares force, and restore a better sense of movement tolerance.

In this client’s case, the story strongly suggested that the left side had become the main bracing side. The left quadratus lumborum was likely helping to hike and stabilise the pelvis. The erector spinae were likely maintaining a protective lumbar strategy. The gluteals were contributing to pelvic control but also becoming overworked in the process. Over time, that kind of pattern can leave the left SI region irritated, sensitive, and stubbornly recurrent.

This is why I often explain it to patients in a very simple way.

Your spine is not only side bent. It is slightly rotated too. Because of that, your pelvis is not sharing load evenly. The left lower back and glute muscles have been working overtime to keep you upright and controlled. They have done their best, but now they are complaining.

That explanation usually lands well because it respects the intelligence of the body. Pain is not betrayal. Pain is often a report.

From a soft tissue and postural correction point of view, these cases are fascinating because they show how the body sacrifices local comfort in order to preserve global function. The nervous system would rather keep you moving with a crooked strategy than leave you beautifully aligned on the floor unable to do anything useful.

So when I see left SI joint pain in a person with a mild scoliosis pattern, I do not see just an ache near the pelvis. I see a rotational chain. I see an asymmetrical ribcage. I see lumbar muscles trying too hard. I see gluteal tissues doing extra stabilising work. And I see a body that is asking for better load sharing, not just louder stretching or random poking.

That is the deeper lesson from this case. Mild scoliosis may look modest from the outside, but its compensations are often surprisingly sophisticated. If you understand the chain, the pain starts making sense.

At JANMI Postural Pain Clinic in Marylebone, this is exactly how I approach these stubborn one sided pelvic and lower back cases. Not as isolated sore bits, but as part of a full anatomical conversation.

Disclaimer: This content is for educational purposes only and does not replace medical assessment, diagnosis, or treatment.

Until next time,

Paulius