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Background

I have been riding a single speed bikes over the last few (8) years in both flat (Perth, Australia) and hilly terrain (Brisbane, Australia). I love riding single speed. It has become part of my identity. I used to joke that I'll get gears when I'm 40. I am 39 now.

I estimate that I ride 5000km/year now.

I am considering switching to a geared bike in big part because I'm concern that it affects my knees and the symptoms will appear in few years.

I don't have knee issues of any kind at the moment and I can get to top 10% of riders on Strava on many segments. Top 20% is often easy. What I am trying to say here is that I like to push and ride as hard as my abilities allow me and that I am fit.

My daily commute involves few >10% gradient short hills (<60s effort) and I like riding these hills up. I go longer way to work to ride more hills.

Ocassionaly I ride a 7% gradient hill with about 9 minutes of effort. It's hard and rewarding.

I often take pleasure (after) riding hills seated with low to sometimes very low cadence.

There is quite a lot of opinion out there about knees and the effect of low gearing.

Question

What is the truth about knees and using low gears (i.e. low cadence, high pressure)? Is there a consensus about its negative effect on knee health especially long term?

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    If it works for you, then you're lucky. I'd be curious to know how your knees/legs feel after a good long steady climb of 30-60 minutes – Criggie Apr 17 '18 at 6:14
  • Thank you for your comment, but I don't think it's relevant to the question in any way. – tymtam Apr 17 '18 at 7:36
  • When going uphill high cadence and low pressure put less strain on the knee joint (and the muscles). Meaning you'll have a small ring at the front and a big cog at the rear. – Carel Apr 17 '18 at 8:31
  • The main thing causing knee problems is having your seat too low. You should be getting almost full extension of the knee at the bottom of your stroke. Other issues of bike fit can also contribute. But having a cadence below 40 or so is also more dangerous to knee health. (Note that both of these problems are common among newbies, where many knee problems appear.) – Daniel R Hicks Apr 17 '18 at 12:18
  • @DanielRHicks Thanks your comment. You present a number of strong claims: 1. seat height, 2. bike fit, *3. cadence <40, 4. many knee problem appear in the newbie stage. Could you provide any references or sources for these claims? – tymtam Apr 20 '18 at 7:12
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Knee issues are mostly a symptom of bad pedalling mechanic (over extension, misalignment, imbalance, that sort of thing). Low cadence "grinding" does not fundamentaly change that unless you start altering your pedal stroke as your cadence goes down.

Note that for fixed gear riding, you also need to consider how very high cadence (descending) may also alter your stroke. In terms of knee problems, fixed gear skids are another potential knee pain inducer as most people will bend one leg inward to get leverage against the frame.

So in short, if your pedal stroke is sound, riding at low cadence should not represent a higher knee injury risk.

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    So is there no effect of the higher compression of everything in the knee joint whatsoever? I mean, just anecdotally, but if I ride the exact same route in the same gear and speed, I can tell the difference in head wind by the amount of pain in my left knee. Assuminging I don't change pedalling mechanic when the wind changes, something else must be at play? – stijn Apr 17 '18 at 11:55
  • At low cadence, pressing harder on a bad knee, or a knee that wobble sideways, or any other bad mechanic is likely to exacerbate the issue. All I'm saying is that this is all linked to the underlying bad mechanic (or already damaged knee). Maybe it's time to get a bike fit? Guetting your saddle height just right is the first step. All in all, stresses on your knees cycling will be an order of magnitude less that while running for instance. Anedoctaly, I do 6000+km/year fixed and even more geared without issues (I never skid and use a front brake!). – zeFrenchy Apr 17 '18 at 13:28
  • Not disputing your answer, but if possible could you provide references – mattnz Apr 17 '18 at 21:17
  • For example, this bit of science (academia.edu/237241/…) says you can reduce pain by increasing cadence but does not says low cadence causes the injury! – zeFrenchy Apr 17 '18 at 21:27
  • @zeFrenchy - I really think you hit the nail on the head with "All in all, stresses on your knees cycling will be an order of magnitude less that while running for instance." – tymtam Apr 20 '18 at 7:06

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