I know that crank length has been talked about ad infinitum, but it's hard to get a definitive answer. Will a shorter crank length help my crappy knees? Or is the whole thing a lot more complicated than that?
also interested if anyone knows?
one thought is a shorter crank arm will mean shorter range of motion, which will either help in the long term, or put your knee under more strain short term.
I think it pretty much depends upon what the problem is.
I have floppy ligaments and find I get on better with longer cranks, though 175's are OK and I've got used to them switching to 170's can cause pain, but it depends on what I do with the saddle to compensate for the lack of 5mm at the bottom of the downstroke. (either move it back or raise it, or a bit of both)
180's were nice, but felt kinda gangly pedalling bigger circles...that was on a SS though so high cadence.
hypermobile knees which have seen the knife a few times here 🙁 When I started track riding earlier this year on 165's my knees were really sore. Got used to them eventually and don't now really notice whether on 165's on track, 172.5's (road) or 175 (mtb). Remember also that shoe/cleat/pedal profile can be 3 or 4 mm difference too
Switched from 175 to 170s and found it really helped, problem practically went away. But I still get issues on a different bike with 170s fitted. Make of that what you will.
Think I find spinning easier with shorter cranks. And the first bike was clipless, the second flats.