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Why are you working on X when my low back is the one hurting?

Hey guys, Robert here again. In my last post, we talked about the prominence of low back pain, especially in the sedentary community. Today, I’m going to explain why in physical therapy we might work on completely random areas of your body when your back is the one hurting.

One idea that will paint a clearer picture for you is that joints are designed to be primarily mobile or primarily stable. The pattern alternates as you move up the body, from stable, mobile, stable, mobile, and so forth. Popularized by Michael Boyle, the Joint-By-Joint Model describes how the body’s joints alternate between stable and mobile to maximize leverages, global stability, movement speed, and strength. Deficits in the primary function of a joint will alter the function of the neighboring joints. In other words, if one joint is designed to be mobile but is becomes immobile, the neighboring joints – which should be stable – are forced to become hypermobile to compensate. Here’s an image to show you what I mean:

Credits to

As you can see, the low back’s primary function is stability. However, that’s not where we’re going to look. Instead, we’ll look at the low back’s neighboring joints: the hips and the upper back. According to the joint-by-joint model, both of these are intended to be mobile joints. Yet in first-world culture, sedentary lifestyles are prominent. People sit too long and too often in front of the TV and get tight hips and a hunched-forward upper back. These originally mobile joints become immobile, causing distortion in the adjacent joints. What is adjacent to both the upper back and the hips? The LOW BACK! The low back, which is supposed to provide stability, is forced to move through greater ranges of motion as a compensation strategy. The end result is dysfunction and pain in the lower back.

Now that you understand the joint-by-joint model, it is clear as to why physical therapists emphasize mobilization of the hips and thoracic spine (fancy word for upper back) to treat low back pain. They are merely restoring the intended function of those joints so that your low back can properly express its intended function of providing stability.

In physical therapy, we give you a home exercise program specifically designed to restore proper motion and strength to relevant structures of your body in order to restore mechanical equilibrium. Your ability to carry out the home exercise program in a consistent manner has a large impact on how well you will do in physical therapy and your long-term quality of life.

That’s all I have for now. I hope you found this of value.

Best of luck,


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