Flounce

I just got over Achilles tendinitis that involved some adjustments to my bike fit, I do have a bike fitter. Rode a 300km brevet (188miles) without any achilles issue, so that was great.

However, I've been starting to get some anterior knee pain (achilles was left; knee pain now right).

It seems to me - and I don't know much about this stuff - that typical bike adjustments that serve to improve Achilles pain stress (saddle down and forward) tend to aggravate anterior knee pain (improved by saddle up and back?).

I will be working on some knee strengthening exercises, keep my cadence high and not mash, etc, but I'm also thinking that going to a SHORTER crank arm length can decrease the stress on both achilles and knee, by having a smaller range of circular motion, i.e. less knee bend at the top of the pedal stroke and, simultaneously, less achilles stretch at the bottom of the pedal stroke. I don't care about mild loss of leverage with shorter crank arm.

If I experiment with shorter crank arm, I will need the bike fit re-done and needs the blessing of my bike fitter.

My bike fitter, who is very good and has experience fitting RAAM riders and such, says "no" - crank arm length doesn't have a role in decreasing my anterior knee pain in long distance rides. Yet the experience of many ultra long distance riders on this forum and outside of this forum is that going to a slightly shorter crank arm length is helpful for our goals.

Your thoughts?

Carbonfiberboy 

I wouldn't think you'd need a refit. Raise your saddle by the crank length difference and move it back just a hair. Go for it, see what happens.

Dsprok

The knee flex is less with shorter crank arms.