Q-Ring for Bicycling Knee Pain

This is for the guy who bikes a fair bit, but who finds his knees - or surrounding bits - hurting.

A bicycle is a very efficient mode of transportation, generally the most efficient way of converting human physical effort into motion over the ground. That is, you go farther for a given input (compared to, say, walking, running, skiing, rowing...). But it's not a totally natural movement.

When you repeat that not-totally-natural movement thousands of times, it irritates the knees. When you do it forcefully, the irritation is worse.


It's that circular motion. It seems nice and smooth, until you examine it. In reality, the crank and pedals are going around in smooth circles, but your legs are trying to pump up and down like pistons. Really, you are pushing at the ends of levers (the crank arms) to cause motion at the other end of each lever. Your muscles and simple mechanics ensure that you get maximum usable work done on the downstroke, and almost none on the upstroke. In particular, there are "dead spots" in the rotation when the pedals - and your feet - are at the top and the bottom of the circle, switching over from up-stroke to down-stroke and vice-versa.

Now think about how the power is transferred.

  • You are pushing the leading pedal (whichever one that happens to be at any given moment)
  • to twist a lever (the crank arm) around a pivot (the axle through the bottom-bracket),
  • which is in turn twisting another lever (the radius of the crank wheel, that extends from that crank axle out to the teeth on the rim of the crank ring).

Which is a problem because...?

The bottom of the pedaling motion is not a big deal. The pressure comes off your foot and knee and your foot is just carried by the motion of the pedal through the bottom dead spot and up the back of the pedaling circle. The problem is the dead spot at the top of the circle.

When your foot arrives near the top of the pedaling circle, your knee must change direction and immediately apply the maximum effort to overcome any inertia and get into that short down-stroke (the power stroke). It's those dead spots, and that transition where you exert to launch the next power stroke, that put a hurt on your knees.

The solution!

The people at ROTOR had the bright idea to modify the geometry of the crank levers (the drive levers) with respect to the driven levers (the radii from the center out to each tooth) by causing the beginning of the power stroke to happen a little later in the circle.

We don't need to know about their early designs, which worked, and were mechanical marvels and very expensive. What concerns us here is the version that they eventually arrived at, some years later - the ROTOR Q-Ring.

It's simplicity itself. Instead of being round like an ordinary crank ring, the Q-ring is an oval or elipse. Instead of the usual fixed set of holes where the crank ring bolts to the rest of the crank assembly (the crank arms and the axle), the Q-ring has sets of holes or has slots, allowing you to bolt your Q-ring with more or less forward "lean" of that non-circular ring.

To wrap up a long story, when you pick the right set of holes for the correct-for-you advance of the pedaling lever action, you displace and minimize the dead spot of the pedaling motion. This takes much strain off your poor knees, and they thank you for it by not hurting.

The company is called ROTOR, and the product is the Q-ring, and you need to order the right size and bolt pattern for your existing crank-set, or you can order a complete replacement Q crankset... or just go to your friendly, neighborhood LBS (local bike shop) and have them take care of it for you.

How much?

A single ring costs a bit over 100 bucks - not cheap, but worth every penny in the opinion of MHT. A multi-ring Q set, as most people would need to replace the usual 2-, or 3-ring crankset found on road and mountain bikes would naturally cost more. So, maybe it's not worth doing on a cheap bike.

But if you use your bike a lot, regardless of what it cost, and your knees are asking for relief, then it might be worth mounting a set of Q-rings that cost as much as your entire bike.

Here's how to get to their site ROTOR Bikes USA If you buy while you are there, tell 'em we sent you. Maybe they'll give us a discount next time we're buying.

If this page wasn't where you wanted to be, then click here to return to the homepage from this bicycling knee pain page.

PLEASE be aware that by using this site you agree to our Terms and Conditions. Save your knees, but risk your sanity by clicking this Terms and Conditions . Knees are more important than sanity anyway.

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