With not much riding going on, I've been consulting every health practitioner's nightmare, Dr Google, to explore the possible causes, implications and solutions for my recent knee excruciations. One useful article on the topic is Knee Pain and Bicycling in the April 2004 (Vol. 32, No. 4) issue of The Physician and Sports Medicine:
Knee pain is the most common lower-extremity overuse problem in cyclists. In one recreational long-distance bicycling tour, 65% of all riders reported knee pain. Another study of more than 500 recreational cyclists indicated that almost 42% of all riders experienced overuse knee pain. While major problems such as fractures, dislocations, and ligament ruptures usually occur only after major trauma, overuse injuries are much more common.
Which is not at all surprising when you consider that:
Cycling is very repetitive; during 1 hour of cycling, a rider may average up to 5,000 pedal revolutions. The smallest amount of malalignment, whether anatomic or equipment related, can lead to dysfunction, impaired performance, and pain.
Or as Dr Will Peveler and co. put it in the Journal of Exercise Physiology:
Cyclists usually keep their pedal strokes around 90 rev/min or greater while riding. Many rides, as well as races, last greater than 4 hours. This repetitive motion can lead to overuse injuries in cycling. Mellion recommends that overuse injuries in cycling should not only be treated with rest and rehabilitation, but also with adjustments to bike setup. Patellar tendonitis is a common overuse injury in cyclists and is usually associated with a low saddle height. A saddle that is too low can cause over-compression of the knee, resulting in anterior knee pain.
Feeling low
There are several good resources on the web about bike fitting, including Sheldon Brown (of course), Peter White's guide, an article on CAMWEST, and Cyclemetrics has a quite comprehensive list of links.
Statements like this in both papers (and in some other reading) put more credence on my hunch: that my seat has slipped down a bit in recent times.
According to the Peveler team, there are four methods for determining the correct height of a bike seat:
- Hamley
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The distance from pedal axle to the top of the seat should be 109% of the rider's inseam measurement
- LeMond
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The distance from the centre of the bottom bracket to the top of the seat should be 88.3% of the rider's inseam measurement
- The ol' heel-toe
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Sitting level on the seat, the rider can just touch the pedal with their heel with the leg fully extended
- Holmes
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At the bottom of the stroke, the knee should be bend 25-35% from straight (which appears to be backed-up by some pretty sound biomechanics)
Peveler's paper set out to see if these four methods for setting seat height actually agree, and they found that the Hamley and LeMond formulas often do. However, they also found that the heel-toe method more often gets the rider into the 25-30° sweet spot, although the range of angles this method produces is pretty wide.
Running the tape measure
While they recommend the Holmes method, we don't all have a goniometer-wielding biomechanist on hand to measure our knee angles, so for me it would have to be one of the other methods.
I've always used the heel-toe method and I've never had any problems before. Other than that, it puzzles me how you can set seat height without taking into account the crank length, so I leaned more towards the Hamley formula than LeMond's. When I did my sums LeMond said my seat was 2cm too low and Hamley said it was a wild 5cm too low. And a check of the heel-toe length showed that my seat height had slipped a bit without my noticing—about 2cm, as it turned out (I know, I know—I shouldn't have let that happen). I don't quite know how, but for me on this particular bike the LeMond formula is pretty effective, so full credit to the TdF champ—he obviously knows whereof he speaks.
I took my newly LeMond-ised bike out for a spin this afternoon, and it definitely felt better with only the odd twinge from the knee to remind me that, yes, I have actually injured myself. But several hours later, the verdict seems to be that the bike is fixed but the same cannot be said for my knee. And given that I have been doing harm to myself over what must be several weeks since I foolishly allowed my seat to slip, I guess I shouldn't expect it to come good in an instant. I hope recovery won't take too long, but I can't say that I'm turning cartwheels of delight this evening. (I'm even considering going [shudder] swimming just to try to keep some muscle tone.)
Now that is interesting: that seat height measure is called the LeMond method all over the web, but only a few sites go on to record that he got the formula from his coach, one Cyrille Guimard. So I appreciate your help in being one of the accurate ones.
I'm a strong supporter of Peter White's view, that you should use a seat height method as a starting point and fine tune the height as the overall adjustment of the bike proceeds.
For what it's worth, I think many people have latent knee problems that only emerge under a bit of extra stress. Since my previous debilitating knee injury, I've been aware that I have a problem with the way my patellas "track" (apparently they don't run as straight as they should in the groove at the end of the femur). And knowing that I've got susceptible knees, it's my own lack of attention that has led me to the position I'm in now. You can bet your last razoo that in future I'll be giving seat height a lot more attention as part of my bike maintenance routine.
Article in this month's Australian 'Runners World' title "When good knees go bad", interesting reading. Though, my knee has never been any bl**dy good!
Whoa, I'll have to look up that one. But I'm the same: the knees weren't that good to begin with…
I'm a bit late to the party, but yes 2 cm makes a ton of difference in knee issues (for some, mm make a difference). The variety in seat height measurements (as others have said you have to judge your own best height for yourself) is often due to how one's foot is positioned on the pedal as one pedals: are you a tip-toe pedaler with your heel up? If so, your effective leg length is much longer than your inseam would let on, and you will have more knee bend (which can translate to more pain). Are you more of a flat-footed pedaler with your foot more parallel to the ground? If so, then your effective leg length is more similar to your actual inseam and knee bend will be less. Those are the things that cause havoc with formulas.
Also, the relationship of your knee to your bottom bracket matters (drop a plumb line from your knee while your crank is parallel to the ground and your foot is in the pedal forward of your bottom bracket)...most want the plumb to bisect or be a cm or two behind the BB -- it would be best to read up on this to know from which part of your knee to drop the plumb, and/or take your ride to a shop to help.
The best fit I got wasn't from cut and dried measurements (i.e I did a Fit Kit), but was from someone eyeballing my legs as I pedaled -- he asked me what was going on, combined that with what he was seeing, added his knowledge to the mix and I left with a "fix" of the achilles problems I'd been having. That said, we set my seat height while working with my pedaling style (tip-toe-ish) rather than from how my foot SHOULD BE positioned.
Good luck!
I ran into woowoowoo yesterday and he was telling me about his new commuter machine. He reckons in the first few weeks he found himself constantly stopping to make little tweaks and adjustments but now he's got it just right. He reckons it's the most comfortable bike he's had.
And likewise with what TOB says. That reflects the good advice that you get from knowledgeable people: use the formulas as a starting point but don't leave it at that. You've got to fiddle a bit to get everything right.
Comments
I think that the .883 of inseam length figure originally comes from the old Cyrille Guimard sizing method from the 70s. Guimard was the directeur sportif for teams that included Bernard Hinault and Laurent Fignon, so he had a pretty good track record before he helped LeMond to find the right position on the bike. Anyway, I am already starting to get off on a tangent, but I think the .883 figure is still somewhat relevant.
An orthopedic surgeon told me that I am susceptible to repetitive motion knee injuries because my kneecaps are positioned high. When I experience any knee pain, it is always in the front directly behind the kneecap. Raising my saddle has helped my situation tremendously. My current road bike saddle height is based on trial and error, but it turns out to be higher than 88.3% of my inseam. All of the sizing methods give you a good starting point, but I firmly believe that trial and error is the only way to find the exact height that works for each individual. Hopefully, raising the seat will work for you as it has for me.