New location

Come on over to my new site:

Going to be posting regularly there.

Monday, June 1, 2009

Front of the knee pain, but first....

Someone asked me a good question the other day:

By writing this blog, aren't you worried about giving away the bike fitting secrets that you've learned and inceasing your competition?

I guess I never really thought about it that way. To me, it's like an architect being worried that by explaining to his clients how their house is drawn up, then they'll use that information to finish the project on their own. There is just too much to know, and most folks, while they may find the information interesting (and I hope everyone does -- I know it can be a bit dry, but we are all nerdy cyclists at heart, and this is the stuff we love to read about), it's not likely anyone is going to be able to read my blog and open up shop on their own based solely on this information. I think it's important that there are practitioners of bike fitting out there that are taking the process more seriously, and treating it as it should be treated -- a very complex, biomechanics-based area of study, and not just a bike shop service.

So now onto the technical stuff.

One of the most common problems I see on the bike is frontal knee pain. Sometimes it is a force issue (just pushing too big of a gear for too long)

(brief diversion)
****I frequently get front of the knee pain (on the right) as I get back into riding shape. My seat height is good, I sit fairly straight on the saddle (see HERE); so what's the problem? As you can see from some of the biofeedback studies we did HERE, when I am not fit, my pedal stroke is not very efficient and I tend to be right leg dominant (like most of the population) AND I am very quadricep dominant when re-learning my pedal stroke. I am just pushing too much with my right leg and the choppy nature of my pedal stroke is requiring more of my quads, so my kneecap and patellar tendon are under tremendous strain.****

(and we're back...)
, but it can also be a patellar tracking issue, IT Band problems (and, incidentally, patellar tracking and IT band sometimes are not mutually exclusive), increased patellar compression/chondromalacia, or even referred or radicular lumbar pain.

The common "fix" you hear about with front of the knee pain is that your saddle is too low and raising it is necessary. Many times this is the case, but it becomes less likely when the pain is only on one side. (If you have a leg length discrepancy or your pelvis sits skewed on the saddle, the seat height may be too low for one leg and perfect or too high for the other leg; in this case you have to figure out why you aren't sitting symmetrically on the saddle first, and fix that)

So if your seat height is okay, where to next? One often overlooked area is how we toe in and toe out. In much of the research it is called inversion (toeing in) and eversion (toeing out) which on the bike is a little different than the motion we refer to as inversion and eversion in biomechanics. On the bike because of how the cleat fastens to the pedal the motion is truly just toeing in and toeing out, but in biomechanics-speak, the toes go in (medially) with inversion, but the bottom of the foot actually points in (medially) as well; opposite for eversion.

Generally when we invert our feet on the bike it drives the knee and increases what's called a valgus force on the knee (valgus = think of looking at the knee straight on and a force presses on the knee from the outside and forces it into a "knock-kneed" position). Conversely, when we evert our foot, we increase the varus force through the knee (think "bow-legged"). This valgus force at the knee essentially takes the ever-important medial quads out of the equation more. These medial quads (vastus medialis and a bit less correctly, VMO) are important because they need to be adequately active to keep the patella in between the two notches at the bottom of the femur. If the patella is not lined up then the underside of it gets dragged against the lateral notch and can cause cartilage damage and pain. The valgus force at the knee puts the medial quads at a mechanical disadvantage. Everting the foot a small amount may reduce this valgus force, and consequently allow the medial quads do their job and/or aid in patellar tracking.

All of this can be read in a great article by Gregersen, Hull, and Hakansson in the June 2006 Journal of Biomechanical Engineering:

How Changing the Inversion/Eversion Foot Angle Affects the Nondriving Intersegmental Knee Moments and the Relative Activation of the Vastii Muscles in Cycling by Gregersen CS, Hull ML, Hakansson NA

I have many clients who have front of the knee pain and the simple act of toeing their foot out (eversion) sometimes helps. Some clients can feel it "unlock" or "unload" their knee almost immediately.

So this is a good option to try if you are at a loss for your knee pain. Just keep in mind that like a lot of things in bike fitting, very tiny corrections are necessary most of the time. Also, remember that when you are changing cleat/foot position, you have to think in opposites: if you want to toe your foot out, you have to toe the cleat in.

But keep in mind that the consequences of toeing out (decreasing the "knock-kneed" force etc.) is what often, but not always, happens. Because we are all just experiments of one we cannot take this as the only consequence. I have, in fact, had some clients who show signs of an increased valgus force about the knee when they toe out. In at least one case it was due to some odd midfoot mechanics, but this cannot be discounted -- there are other people out their with these same mechanics and there are most certainly other movement asymmetries that could cause this eversion/varus relationship to break down as well.

1 comment:

  1. I really liked your blog and would like to know more about the topic
    buy viagra
    viagra online
    generic viagra
    thank you very much..