5' 4"
170mm factory-issue on GT Mtn

6 mos later, after "car vs. me" incident, the LBS (s) didn't have 170's to fit & I was off to Vancouver (from Toronto) w/ 175's instead.
Naively didn't know any different, so said "ok, 175's fine"... yet no probs in Vancouver despite hills + 8 hr days on the bike...
Back to T.O., switched to SPD's (great!float ok, super-duper fun etc.) but: 3 mos. later Knee Probs, taking me right off the bike ... for months sigh ...

Then, GT recall on crank set, shop now had 170's again, so went BACK to 170's.

Many calls to Different Shops here have resulted in the speech: "165's? 167.5's? Uh .... lady, those are hard to find..."
Note: I'm not looking for fluorescent polka-dot fun-fur custom cranks. But still, this response. I take my business elsewhere & same thing happens..?
Since I'm not overly mechanically minded, I do not know if whatever crank set (ordered on the 'net for instance) would fit the bike's BB etc... Among a zillion other Q's I suppose ...

ANYWAY:
Sill knee probs... surgeries...gave up for a while (a few years)... now, back in "Stubborn/Optimistic/Delusional(?) Mode", trying to figure out what the KEY(S) to this PUZZLE could be. I say "key(s)" since I've tried what seems to be everything under the sun. Any other types of leg-based exercise (running, weights, etc. = zero knee probs). On-the-bike puzzle though, you name it, I've most probably tried it.

Hence the CRANKS POLL Questions.