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Dr. Cathy A. Kim, MD, APC

The Role of the Legs in Back Pain | Ep. 7

The Role of the Legs in Back Pain

The Role of the Legs in Back Pain | Ep. 7

In this video I am using a functional medicine approach to help you understand the connection between your fascia, thighs, and lower back pain. Watch the video or read the transcript below to learn more.


Hi, I’m Dr Cathy Kim and I’m a Body Function Specialist.

In my Functional Medicine practice, I help you understand how our modern lifestyle is causing inflammation and inflexibility in our bodies. I then educate you on the most meaningful changes you can make to restore well-being.

In my last video, I explained the importance of the pelvic floor muscles in assisting the back.  

Today, I want to demonstrate how our thigh muscles can strain the back, and how improving their flexibility can reduce back pain.

Here is the model of our pelvis, the orange tape showing us the orientation of the pelvis when tilted (A for anterior; P for posterior), the pink tape representing those overworked back muscles, and the yellow tape representing the lifting action of our pelvic floor muscles.

I’ve added blue tape to represent our thigh muscles, which attach along the bony border along the front of the pelvis. On one side, I have flexible thigh muscles, and the other side, stiff muscles. 

I am using my arm to demonstrate the action of our front thigh muscles as we stand and sit.  Imagine my elbow is actually my knee. To straighten my knee, my front thigh muscles, the quadriceps, contract, while the underside of my thigh, the hamstrings, elongate. When I bend my knee, I contract my hamstrings, while my quadriceps muscles stretch.  

Most people are very surprised to realize that standing only stretches one side of the thigh, the back or posterior site, not the entire thigh.  For any given position, one group of muscles is stretching, while another group is contracting. Prolonged periods in either position ends up causing imbalances between muscle groups, as we will see in the next demonstration.  

Here, blue physio tape helps us visualize what is happening to our muscles and fascia beneath the skin’s surface. 

When we sit, the quadriceps muscles stretch, especially near the knee, while the hamstrings and hip flexors contract. See the wrinkling at the bend of the hip and bend of the knee?

When we stand, the quadriceps muscles contract, while the hip flexors and hamstrings stretch.  Note the slack in the tape above the knee.  

With repetitive prolonged sitting or standing, these understretched areas of our fascia start to remain contracted and restrict movement.  This is because our fascia behaves like physio tape, not duct tape.  

When duct tape folds on itself, pulling on the ends transmits the force along the stiff tape to unstick the tape.  But when physio tape folds on itself, tension on the ends only translates into causing the rest of the tape to stretch more.   

Regular, diverse movements can help us maintain flexible and functioning fascia, but for most of us, it won’t be enough to open up the past areas of contracted and scarring that we have accumulated. This is why simply switching to a standing desk is not a long term solution for low back pain.  

Myofascial release bodywork is an important adjunct to restoring balance to the musculature of the body, simply stretching or switching positions will not open up these problem areas. 

Now let’s return to the model of our pelvis, and try to imagine how stiff thigh muscles can dictate the forces around the pelvis. 

During standing, the contracted and stiff anterior thigh muscles exert downward traction along the front of the pelvis, which forces the back muscles to stabilize the torso. 

While seated, flexible thigh muscles are able to stretch all the way from pelvis to knee, but stiff thigh muscles cannot accommodate the necessary stretch, they pull on the pelvis, which makes the back activate to oppose this force. After prolonged sitting, the back muscles fatigue from compensating, and then we feel pain or discomfort.

With exceptionally shortened and stiff thigh muscles, the thigh muscle tension will require a posteriorly tilted pelvis. These individuals cannot access their back pockets while seated because the pockets are completely underneath them.

Please note: Our fascia has more pain receptors than our skin. It can be surprisingly painful to work on contracted fascia, so you have to be kind and patient with yourself. In general, the more intense the pain, the more dense your fascia is at that location.  

Some of you may already be thinking, what is the point of going through the pain of opening up contracted fascia if it’s just going to return to the way it was?  

This brings us to the topic of my next video. I will demonstrate how I teach patients to make the most out of their everyday movements to promote length and elasticity of the thigh fascia.

If you have any questions or suggestions, please let me know in the Comments. Thank you for watching. 

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Dr. Cathy Kim

Dr. Cathy Kim is a Board-Certified Family Medicine physician and Body Function Specialist. She practices in Camarillo, CA and specializes in complex cases.

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