How Knees Work (And How to Make Them Work Better)

Knees get a bad rap. Of the top seven most common sports injuries, three of them are knee-related. Even for non-athletes, creaking, popping and aching seem to be practically inevitable.

I used to buy in to the conventional wisdom that knees are poor shock absorbers, cursed by design with an inexplicable fragility.  I’ve since realised that this is like failing to drive a nail with a bullwhip; yeah, it makes a poor hammer—but “fragile” isn’t exactly the word I would use.

Not pictured: fragility.

If you’ve read just about any of my other articles, then you’re well aware of the super-cool, force-muliplying function of your foot and ankle. All of that force, which winds up as internal rotation of the tibia, has to somehow get to the pelvis as external rotation so that it can be used as propulsion for our center of gravity.

Rather than a shock absorber, The knee is the adapter which allows that shift to happen. When your knee bends, your once-straight leg gets shorter, meaning that any force applied to it suddenly moves the whole structure faster through space. It’s the same principle ice skaters use when they pull their arms and legs in and magically start spinning at 300 rpm.

This increase in velocity is stored as elastic tension in your hips; when released, this turns your femur into a trebuchet, propelling the pelvis forward.

A trebuchet. Also, the only response necessary if someone asks: “what’s so cool about physics, anyway?”

Blah blah physics and bones and stuff: you’re reading this because your knees hurt, not because you’re looking for a science fair project.

Pain in the knees is typically associated with a force acting on the knee, rather than passing through it, like it’s supposed to. Because the knee is situated between two joints, this means that one of those joints is doing a poor job of receiving the force exiting the knee and reacting accordingly. The video below is an exercise for identifying and correcting that relationship.

There are two things you need to know:

1) Your dominant leg and non-dominant leg behave differently—and, barring a few rare exceptions, behave similarly to everyone else’s dominant and non-dominant legs. (Roughly 70-90% of you prefer your right leg.) Before watching the video below, identify your dominant leg by kicking a football (or imagining kicking a football) and noting which leg feels most natural.

2) Certain types of footwear—in particular footwear with “arch support” or some kind of orthotic—may prevent this from working properly. Unless under specific, recent advice from a doctor to the contrary, take your shoes off when you do this.

You may notice that I didn’t show the exercise in reverse, with the dominant leg in back. Of course, feel free to play with that position, but, in my experience, building up the necessary strength and awareness happens best in the format presented. Because the goal of the exercise is an internal relationship within the leg, symmetry across the two sides is not necessary.

Think of this as an experiment rather than an exercise regimen: repeat it frequently but without intensity. Performing the movements described will give you a better feeling for what muscles you’re not using when it comes time to fire up those knees. As you become more aware where strength is lacking, try performing simple daily activities like climbing stairs, kneeling down, jumping and squatting with an emphasis on the movements and muscles you now know aren’t doing their fair share.

Have fun and let me know how it goes in the comments!