Key Points

• The quadratus lumborum and psoas muscles are antagonistic yet have an interesting codependent dynamic.

• Sink into the thoracolumbar aponeurosis and erector spinae group and continue to slide anteriorly until you palpate the convergence of where the QL meets the psoas.

In a recent podcast episode (Ep 147 – “Old Man Psoas”: The Rebel MT with Allison Denney, www.abmp.com/podcasts/ep-147-old-man-psoas-rebel-mt-allison-denney), I compared the quadratus lumborum (lovingly referred to as the QL) to being the youngest kid in a large family of muscles. Flanked by the erector spinae, blanketed by the thoracolumbar aponeurosis, and responsible for a whole lot of core movement, it can get cranky from doing too much and yet constantly being ignored. But there is another relationship the QL is in that deserves some attention, and, in reality, probably a little therapy too.

For as long as it can remember, the QL has been coexisting with the psoas. If we take a closer look at where each of these muscles latches onto the bones they move, you’ll notice they share gripping points. The transverse processes of the lumbar vertebrae—otherwise known as spine pegs—protrude from the sides of the lumbar vertebrae and make the perfect handhold for both of these deep-core muscles.

While the QL lingers in the background and clings onto the last rib and the iliac crest, the psoas lies just in front, nestled up to the bodies of the lumbar vertebrae before it drops down and finds the lesser trochanter. And, although the QL is considered a low-back muscle and the psoas is considered a hip flexor, what you may not realize is they share the blanket of connective tissue that surrounds them both and binds them into an interesting dynamic.

These two thick muscles are commonly talked about in isolation and not very often discussed in terms of their relationship to each other. Like two married Hollywood movie stars who suffer because they spend most of their time apart, these two are more like a dysfunctional marriage than you might think. They are together, yet separate. They are united, yet divided. They are dependent on each other, yet completely, disjointedly codependent.

Together Yet Separate 

Let’s look at the most basic element: they are antagonistic muscles. The QL is responsible for trunk extension and the psoas is in charge of trunk flexion. This means they cohabitate a very small space but constantly want to do their own thing. And while we may see a myriad of examples of antagonistic muscles fighting over a joint in the body, the unique aspect of this relationship is they exist in the most centrally core part of our physical bodies. So, the irritations and frustrations that arise from these two not getting along become problematic on a much deeper level.

Low-back pain is an epidemic that is chronically blamed on the QL. This fact, coupled with the general confusion and prevalent trepidation around working with the psoas, has clouded the work that can be amazingly effective in this area. The knowledge that they share a significant layer of fascia yet conflict in what they are trying to do is an invaluable piece of information you can start using to your advantage.

Think about this: The QL is working tirelessly to hold us upright, to straighten our spines from a bent position, to hike our hips up while we walk, and to hold our rib cage in place when we breathe deeply. At the same time, the psoas is cinching us into a seated position, pulling our legs up so we can rest one ankle on the opposite knee, and slowly becoming accustomed to short spurts of slight activation when we drive. These are clearly oversimplified examples, but the idea is this—the QL tends to work tirelessly. The psoas commonly doesn’t pull its weight. And the codependent relationship that has evolved is toxic and needs an intervention.

Getting to Work

Accessing where these muscles converge is the key. With your client prone on the table, thoroughly warm up the thoracolumbar aponeurosis and the erector spinae group. As you start to sink deep to these, and into the lateral aspect of the QL, continue to slide anteriorly until you can palpate the convergence of where the QL meets the psoas. Once you are there, have your client create slight posterior and anterior pelvic tilts. This might be tricky for them to grasp, so try asking them to push their low back into the table and then lift their belly up away from the table. Remember that these movements do not need to be grand, just enough to get the muscles to engage.

Have your client repeat these subtle movements and you will start to home in on where the QL ends and where the psoas begins. You will also gain a greater awareness of how well they are, or are not, communicating with each other. And, most importantly, you will begin to shine a light on what exactly is going on for your client. Perhaps the QL is overbearing. Perhaps the psoas is shy. Perhaps they have lost their way and just need to find each other again. In any case, you have opened a line of connection that has been lost, and that, my friends, is the beginning to healing for any wounded relationship.