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Home > Chronic Pain > Knee Pain > Knee Popping

Knee Popping and the Vastus Medialis

The Vastus Medialis and its Role in Chronic Knee Pain and Popping or “Clicking”

Why does my knee pop?

vastus medialisKnee popping or clicking usually has a very simple explanation: your knee cap isn’t tracking properly in the joint.  Here’s the deal: your quadriceps (the muscle group on the front of your thigh) is made up of four muscles.  Your knee is popping because two of those four muscles are in a tug-o-war over your knee cap and one of them is winning.  The two muscles causing the knee popping are your vastus lateralis and your vastus medialis.  The vastus medialis is on the inner-front part of your thigh and the vastus lateralis is on the outer-front part of your thigh.  These two muscles connect on either side of your knee cap.  In some people, for whatever reason, the vastus lateralis gets too strong or the vastus medialis gets too weak.  As a result, the knee cap is pulled too far to the outside by the overly strong vastus lateralis and as the knee moves the knee cap isn’t gliding properly in the trochlear groove, causing knee popping, clicking, snapping, and other similar noises and sensations.  In a healthy knee, the relative strength of the vastus lateralis and the vastus medialis is balanced and the knee cap slides up and down in the trochlear groove as it’s supposed to.

How do I tell if this is what’s causing my knee popping?

knee poppingThe short answer is: it’s difficult.  Trial and error is probably the best method.  There’s one thing you can try, however.  To determine if your knee popping is caused by your vastus lateralis overpowering your vastus medialis sit on the ground with your legs out in front of you  and something to support your back.  Rotate your legs so your toes are pointing toward twelve o’clock as you look at them.  Your kneecaps should now be pointing toward the sky.  Totally relax your quadriceps if you haven’t already.  Now reach down to your non-popping knee and try to very gently move that knee cap left and right with your thumb and forefinger.  Pay attention to how much it moves, how much “play” is in the knee cap.  Now repeat for the knee that pops.  If the knee that pops has more “play” in it, that’s a strong indicator that this is your problem.  Even if you can’t tell the difference, that doesn’t mean this isn’t your problem, however.  If you can’t tell the difference then the only way to diagnose yourself is trial and error.  Try the exercise prescribed below for a couple weeks and if you don’t get any results, this isn’t the cause of your knee popping.

How do I fix it?

The good news is that knee popping can be semi-permanently fixed in a week or two.  You should do two things to fix knee popping.  First you need to strengthen the weak vastus medialis so that it can hold the knee cap in its proper place as your knee bends.  To do this, you will simply perform an isometric contraction of the quadriceps muscle group.  Sit on the ground with your legs out in front of you and something to support your back.  Rotate your legs so your toes are pointing toward twelve o’clock as you look at them.  Flex the quadriceps on the knee that pops.  You should see muscles on the top of your thigh move around.  Reach down and poke your vastus medialis to better innervate your vastus medialis before each contraction.  This will give you a stronger contraction.  Flex the quadriceps and hold for 10 seconds and then relax for 10 seconds.  Repeat 10 times 1-2 times per day for several days or as much as 2-3 weeks.  This exercise works the vastus medialis because the vastus medialis works the hardest during the first 10 and last 10 degrees of knee flexion (i.e. when your knee is almost straight and when your foot is almost touching your butt).  An exercise called the standing terminal knee extension is an alternative to the one described here.

Second, you should strengthen your hamstrings.  The hamstrings are weaker than they should be in anyone who sits down for long periods every day.  Physiologically speaking, given a sedentary lifestyle, women are more prone to have weaker-than-optimal hamstrings than men.  Strong hamstrings will help with knee popping because strong hamstrings help to ensure that your femurs are not rotated too far out or in and are an important part of knee health.  The one of the fastest and easiest ways to strengthen your hamstrings is to do an exercise described on floota.com, the supine bridge.  As an added benefit, this exercise will strengthen your gluteal muscles (butt) as well.  Perform two sets of 20-40 repetitions every other day until your knee popping resolves.
That sums it up: knee popping can best be fixed by isometric contractions of the quadriceps and concentric exercise of the hamstrings.  Viola, your knee popping is gone.  Unfortunately for many of you, you will have to do these exercises periodically for the rest of your life if and when your knee popping returns.

Why can’t I just do traditional quadriceps exercises to fix my knee popping?

I’m not going to BS you, I don’t know.  In my experience experimenting with my own knee popping, concentric quadriceps exercises like stair climbing and running actually make the popping worse.  I hypothesize that the knee popping gets worse as a result of these exercises because they strengthen the dominant vastus lateralis more so than they do the vastus medialis, exacerbating the imbalance.

Further Reading: Related Floota.com Articles

  1. ITB Syndrome
  2. Calf Self-Massage with a Tennis Ball
  3. ITB Stretch
  4. Hamstring Stretch
  5. Quadriceps Stretch


  1. 18 Tips for Bulletproof Knees, by Mike Robertson
  2. Runner’s Knee @ merck.com
  3. Brunnstrom’s Clinical Kinesiology, 323 (5th Ed.) (detailing patellofemoral joint forces).
  4. Standing Terminal Knee Extension Exercise @ youtube.com

Last Updated: 6/1/2011
Originally Posted: 2/9/2009