IMO the knee issues are not related to the bike, but rather the fit or setup of the bike. You'll have the same potential issue with any bike or frame geometry regardless of frame size. Which bike geometry or style "feels" the best is a subjective matter that you'll only sort out riding each bike. Back to bike fit, there's a whole section here on BF devoted to bike fitting. My wife and I both had GURU dynamic bike fits last winter. My wife also complained of knee pain after even short rides. The bike fit completely eliminated this - and interestingly, the new bike setup was a more agressive riding position. This resulted in faster riding, more comfortable, and no knee pain. Everything was a win. If you're LBS doesn't have a GURU system, google it. It's amazing.