Today, I found out that the frame of my touring bike was few size small for my height. I am 5' 8" (33" inseam) and ideal frame size for my height should be 21" whereas the frame of my bike is, I am afraid, only 17". And I can't find a replacement of this frame (it is always hard to find a hybrid frame replacement, they do come with the bike itself or they never come. Also it looks a bit weird like a MTB frame, maybe it is an MTB frame, who the hell knows?)

Do you think I can compensate the difference by hightening the saddle (because this is what I am doing now)? Even though I did this adjustment I can't feel much comfortable on the bike and it might be the reason why I am dealing with knee issues since two years.

You can see the bike in attached photos, saddle height is much higher now, these are old dated pictures.