Low back pain is one of the most common complaints we see as Physical Therapists. There are a multitude of symptoms that can accommodate a low back pain referral, but the one I hear most frequently is, “My back feels tight.” Often times a patient will point to either side of their spine with these complaints. They are able to get some temporary relief with stretching, but the pain seems to keep coming back.
The muscle that commonly leads to these subjective complaints is the quadratus lumborum. The quadratus lumborum, or QL, originates at the iliac crest and inserts at the 12th rib as well as the transverse processes of the lumbar vertebrae. Traditionally, we have viewed the QL’s primary function as being a lateral flexor of the spine, but the QL has another important role that doesn’t get as much recognition.
Frontal Plane Mechanics During Absorption
To better understand the role of the QL during the gait cycle, let’s examine the frontal plane mechanics of the pelvis, specifically during the stance phase of the right lower extremity. As the right heel strikes the ground, we enter the absorption phase. During absorption, our right hip will adduct and our pelvis will tilt laterally, but only about 4-degrees. At this point in the gait cycle, the left side of the pelvis rests slightly lower than the right. Although excessive pelvic tilt can be harmful and make us a less efficient ambulator, the right amount of pelvic tilt is crucial for absorbing force through the hip. This can also provide us with some cheap elastic energy because the adduction moment at the right hip will create tension in the right hip abductors. This tension is stored as elastic energy and is later released to help us to efficiently abduct and extend the hip as we transition into the propulsion phase of gait.
Now let’s take a look at what muscles are involved that allow these actions to transpire. Traditionally we have viewed the hip abductors – tensor fascia latae, gluteus medius, & gluteus maximus – as the muscles controlling lateral pelvic tilt during gait, but it’s not quite that simple. While the abductors do help to eccentrically control the amount of lateral pelvic tilt, we also require some help from the contralateral side. This is where the QL comes into play. As we discussed earlier, the QL has attachments on the iliac crest, 12th rib, and the transverse processes of the lumbar vertebrae. These attachments put the QL in an opportune position to ensure that the pelvis does not drop too far away from the rib cage. Much like the right hip abductors, the left quadratus lumborum must eccentrically contract during the absorption phase to help control lateral pelvic tilt.
Culprit or Victim?
As you can tell, a lot is happening to ensure the appropriate amount of lateral pelvic tilt is present during the absorption phase. The hip abductors must be strong enough to support the weight of the body while lengthening enough to create an adduction moment at the hip. Too little tilt and we lose out on elastic energy. Too much pelvic tilt and we have energy leaks. But what happens when the hip abductors are too weak to support this process? If the hip abductors lack strength, we will see excessive lateral pelvic tilt on the opposite side. This is known as a Trendelenburg gait. Our bodies, however, are master compensators. One way we attempt to correct a Trendelenburg gait is by recruiting the help of the contralateral QL. Although the QL would ideally eccentrically control the amount of lateral pelvic tilt during absorption, it can also pull up on the pelvis to correct the excessive lateral tilt present with weak hip abductors. This compensation leads to the QL being overworked, which can lead to complaints of low back pain or stiffness. In this case, the QL is the victim and the weak hip abductors are the culprit.
Fixing the Cause
I mentioned in the opening that patients frequently report stretching helps to alleviate their symptoms, but the pain keeps coming back. This is because stretching targets the symptoms but doesn’t address the underlying cause. It’s okay to stretch the QL or perform manual therapy to decrease stiffness and provide some pain relief, but until you treat the culprit, you won’t have solved the actual problem. We need to strengthen the hip abductors.
There are all kinds of ways to strengthen weak hip abductors. For me personally, my favorite way to address this problem is to perform lower body strengthening exercises in single limb or asymmetrical stances. Examples of these exercises include rear foot elevated split squats, lunges, or, one of my personal favorites, touchdowns. The reason I am such a big fan of touchdowns it that they force our hip abductors to function in a way that resembles how they function during gait. The hip abductors are asked to stabilize the pelvis while the lower extremity undulates between triple flexion and triple extension.