You hear it from trainers and doctors, see it on television and in magazines. Weak knees, knees at risk, no strength in knees, etc. The solution? Strengthen your knees. There’s only one problem with that.
You can’t make your knees stronger.
The muscles surrounding your knees, well that’s a different story.
If you look at a picture of a knee joint, you’ll see it is free to flex in only one plane of motion, like a door hinge. That makes sense because it is technically categorized as a hinge joint. But unlike a door hinge, there is no bolt that holds both pieces together. Our knees are held together by a labyrinth of ligaments and tendons, some of which are well known due to their frequency of injury (ACL tears anybody?). Since our knees have the potential to get injured so easily, we often want to find a way to protect them. I’m not referring to athletes who play high impact sports, or acute injuries like ligament tears, but the average person who might hurt their knees going up stairs or making a turn on an uneven sidewalk. Unfortunately the advice we get is worded completely wrong, which usually results in us not getting the results we should.
When your doctor or trainer says “You need to strengthen your knees”, what they really mean is “You need to strengthen the muscles around your knees”. Remember the door hinge? The whole idea of a hinge is to swing freely, just like our knees. But the easiest way to open a door is from the handle, which is about as far from the hinge as you can get (try swinging a door open with one finger near the handle, then try the same thing near the hinge to see how important leverage is). Likewise in our legs, the only thing that can start or stop the movement are the muscles that connect to the femur, tibia and fibula. The knee joint itself is powerless to do anything!
Armed with this information, a person will dutifully go out and do leg raises, leg extensions and maybe even some leg presses to make their knees stronger. They’ll avoid squats since those damage your knees instantly and nobody who’s ever squatted has been able to walk afterwards*. After a few weeks of doing these exercises they may feel a little bit stronger and go back to their former activities. But their knees still hurt, or make noises, or click, or just feel weak.
The reason for this is something that we’ve discussed before, which is displaced emphasis. When the word “knee” was said, the person fixated on the actual joint while doing exercises rather than the muscles around it. Leg extensions were performed with feet locked in dorsiflexion and tensioning of the knee. Leg presses were done by pushing through the toes with hands on the knees to “help”. All of these actions displace the emphasis off the quadriceps and hamstrings which are the prime movers for the knee joint.
If you want to “strengthen your knees”, ignore them. Focus on the quadriceps and hamstrings while relaxing pressure on your knee joints. Never ever ever everrrrrr apply any force directly through the knee joint itself unless you really do want an injury. Don’t know how to keep the force out of your joints? I’ll describe three common exercises, what you should be feeling and how to position your body to get the most out of them.
Hamstring Curl: The prone (face down) version works best for this scenario. Ensure that your hips are flat against the pad and there’s no space between your pelvis and the pad. With the lever pad on the back of your calves, relax your feet completely and squeeze the back of your thighs with the emphasis on your hip/butt region to start the flexion motion. Don’t try to start the movement from behind your knee. Perform as many as are required without letting the weight stack touch between reps.
Leg Extensions: Slide back on the seat until the back of your knees are against the leading edge of the seat pad. With the lever pad against your shins, grasp the handles to pull yourself down firmly against the seat, relax your feet and squeeze the tops of your thighs until your shins “float” up to the horizontal position. Don’t try to start or slow the movement by clenching the knee joint, especially if you’re attempting to do negatives/eccentrics.
Leg Press: Place your feet wherever you want based on what you wish to accomplish (feet high = more hip/glutes, feet low = more quads). Position your back tightly against the seat, dig your heels in and squeeze your thighs to start the motion. Do not put your hands on your knees to help move your legs. As you perform the reps, imagine your hips as a shock absorber on the eccentric, not your knees. Again, do not use your knees to slow down, reverse, push or lock-out.
Again, this article is not intended for people who have legitimate tears or ruptures in knee tendons. While the listed exercises might be included as part of a rehabilitation program, the intent is for reasonably uninjured people to increase the stability of their knee joint without inflicting unintentional damage. After a week or two of doing the exercises as described, your knees will feel a lot…stronger (sorry, had to say it).