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Dr. Cathy A. Kim, MD, APC

Are You a Knee Locker? | Ep. 3

Close-up image of doctor cheking knee of male patient

Are You a Knee Locker? | Ep. 3

As a Body Function Specialist, I employ Functional Medicine principles to both internal and external body mechanisms, in order to reduce inflammation and inflexibility.  

Over time, I noticed that all of my patients had varying degrees of Genu Recurvatum (knee hyperextension), otherwise known as “locking the knees.”  Paradoxically, although their knees (and often other joints) were hyper-flexible, the surrounding muscles were actually inflexible.  

Interestingly, many of these patients (with the most marked Genu Recurvatum) reported suffering since childhood with various joint pains, difficulty falling asleep, and being injury prone.  Many of them started at a young age with conditions usually associated with older adults, such as plantar fasciitis (heel pain), back pain, urinary frequency, and vertigo.  

This video/transcript describes how “knee-locking” results in typical postures from pelvic imbalance and why stopping this habit is key to achieving a more functionally flexible pelvis.


Hi, I’m Dr. Cathy Kim. Founder of Integrative Body Medicine, I’m also a member of the Institute for Functional Medicine and Academy of Integrative Health and Medicine.

This video explains the mechanics of knee hyperextension, and how it increases the hip flexor forces and prevents our goal of a neutral pelvis. 

When you are hyper-flexible, this means that your joints can move past the normal 180 degrees open position. This is most noticeable in the knees, elbows, and thumbs. Some people have it in multiple joints, others only seem to have it in their knees. Many of these people excel at activities such as dance, swimming, and gymnastics. Because more joint flexibility helps them achieve more range of motion and momentum. 

So, who wouldn’t want hyper-flexible joints so that we can do the most advanced yoga poses and swim super-fast, by whipping that flexible body through the water? Well, it turns out that standing locking the knees backwards, can hurt your body over time. It deeply disrupts alignment of the pelvis and causes deep imbalances that can reach all the way to your head and toes. 

To understand better what is happening, let’s look at a kickstand for a bike. When you put the kickstand down it leans on the ground at an angle and then the bike tilts at an angle to lean on the kickstand. This leaning on top of leaning is what happens when you lock your knees backward thus, making your thigh bone, called your femur, not vertical. 

One more concept to understand is about how muscle groups work to make a joint open and close. The bicep closes the elbow, and the hamstring closes the knee, and then the triceps straightens the elbow, and the quadriceps straightens the knee. 

When we stand, we contract our quads, while our hamstrings relax so that the quads can pull the knee completely straight. But, when we stand with our knees locked backwards, our quads stay soft, because we are not using them to straighten the knee. We are just angling the knee backward, and leaning into the front of the hip joint. This leaning adds to the tension forces in the hip flexor. 

In life, we all figure out the fastest easiest way to get things done, brushing teeth, packing, and drinking directly from the carton. Hyper flexible people have figured out that the easiest way to stand, is to lock your knees because they do not have to exert any effort in their thigh muscles. This adds up to hundreds of hours that contribute to hip flexor tension, which is often at the root of many persistent lifelong issues such as back pain, heel pain, even vertigo, and painful periods. 

There are two most common postures that occur as a result of this chronic downward hip flexor tension, and these are best viewed from the side. Let’s call them positive and negative compensators. In the positive compensators, they use their back muscles to strain and lift up against the tipping pelvis, and they end up with a big arch in their back. In the negative compensators, they don’t use their back as much and allow their abdomen to cave inwards as their pelvis drags down the front of the body. 

For you hyper-flexible people out there, there are two ways to stop the cycle of hip flexor tightening. Number one, and this is the hardest one to be aware of the knee lock when it occurs. When standing talking to friends or bending only at the waist to pick up something. By bending your knee slightly in the future, you will help make your femur more vertical and less like a kickstand. Then, your thigh muscles can actually start working and strengthen. And number two, add the Mula bandha from video 2, to your postural transitions.

Since the entire network of muscles was accustomed to this lifelong imbalance. It is very common to experience pain in new and different areas while on your journey of correcting the foundation of your alignment to get to your neutral pelvis. For this reason, rebalancing the muscular function of your entire body usually requires the help of a professional. 

If this explanation of how knee hyperextension exacerbates postural imbalance makes sense to you and you’re wondering what more you can do, please watch my next videos. You can also visit my website integrativebodymedicine.com (now drcathykim.com) to learn more about my approach to whole-body health.

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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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