Originally Posted by
canklecat
I expect it'll feel odd at first, but most folks who've gone to shorter cranks say they adapted.
The success of your recovery from knee surgery is dependant on the amount of flexion (bend) and extension (straightening) you can recoup. Therapy is crucial. My knee flexion recovery was a bit of a disaster and I've had to outfit my bikes with cranks ranging from 128 to 145 mm. You gradually adapt after some previously under-utilized muscles tone up to compensate for the lack of leverage short cranks provide. You can get stronger in different places, even if you're old.
And you can spin like crazy!
OP, that bone-on-bone pain off-bike goes away completely. You'll love it.