I love seeing practical applications of biomechanics that can help patients. For example, yesterday afternoon I worked out at a hotel gym in Orlando. The spin bike had traditional clip-in pedals, which I haven’t used in more than a year. As I felt my weight shift to my quads and kneecap, I knew I had chanced on a great way to teach kneecap pain patients how to avoid frying their knee. Let me explain.
While kneecap arthritis has many causes (click on my infographic to the right), one of them is too much pressure on the front of the knee and quadriceps. This muscle is the main extensor of the knee and has the kneecap (patella) living in its tendon. So what happens when this muscle impacts the cartilage under your patella? Too much pressure over time causes the cartilage to break down and arthritis to set in.
There’s nothing like direct experience to help you understand a concept. So start by standing up and then placing more pressure on the ball (front) of your foot than on the back by slightly lifting your heel. Then squat to about 45 degrees and notice how much the front thigh muscles (the quadriceps) engage. Then compare that to how much your butt and hamstrings engage. Now let’s change things up a bit.
Move your weight back on your heels. To do this, you can pull up slightly on your toes. Now do the same squat and notice what engages. You should feel that your butt muscles and hamstrings engage more. Your quadriceps should be less activated (image to the right).
So in a few minutes, you’ve learned that how you activate the thigh and butt muscles can either hurt or help your kneecaps. Meaning, if you’re relying on your quads (quad dominant), this is going to cause problems. What’s the most common cause of a quad dominant knee that we see in the clinic? A bad back. Let me explain.
When the lower back nerves get irritated, this can shut down the hamstrings and the glutes. Since they’re less efficient, the quads take over. In about half of the patients I see with this issue, they know they have a back problem. Interestingly, in the other half, they don’t think they have a low back problem, but the irritated low back nerves are clearly seen on an exam.
So how did working out on a spin bike in a hotel gym get me on this topic? Last year I switched all of my bike pedals to this model. Why? A patient with patellar arthritis made the switch and swore by them. I then decided to check these out, and the biomechanics made sense, so I tried them on my spin bike. The rest is, as they say, history. However, I didn’t realize how good they were until this spin bike. Why? Let me explain.
Note the image to the right.
When I got on the bike at the hotel, it put the pressure on the balls of my feet. This moved the force up through my quads and made me quad dominant. Which, over time, will burn out my kneecaps. It’s hard to explain just how different this felt than my new pedals at home. These place the force farther back on my foot and throughout my whole foot, which takes the pressure off of my quads and evenly distributes it between my quads and hamstrings.
The upshot? If you want to protect your kneecap cartilage, one thing you can do is to become less quad dominant. Meaning, move the weight back on your heels with squats or change out your bike pedals from the traditional style that place the force under the ball of your foot. Also, check out the infographic above to learn about other causes of kneecap problems. Finally, I have a whole blog dedicated to everything you can do to end patellar pain issues.
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