Not sure if it applies to you, but I have a knee that doesn't bend quite as far as normal (motorcycle down hard years ago).
I found that going to 165MM cranks allowed me to have "enough" range of motion that longer cranks didn't.
Maybe shorter would help you in the fact you don't have to bend your knee quite as far for each revolution???
Also seat height- Every bit that the seat is lower than it SHOULD be results in more bend.