Originally Posted by
Mr. Underbridge
Other non-frame possibilities: you could possibly use a higher stem if you're too hunched over, also you might have the seat too low.
I woudn't worry too much about the standover height. In my experience, if you have a bike with a flat top tube and you can stand over it with both feet on the ground with clearance to spare, the frame might be too small. You'll never stand over the bike like that anyway.
This
Smaller frame is going to mean seat to bar height is going to hunch you over more . I believe you have the correct size frame just not set up correctly especially If you are running flat bars
Any reach issue can be fixed with the stem length and angle. I use to try to do things the other way and buy a frame for the top tube lenght and I ended up with seat way up in the air and hunched way over aggravating problem Have in my lower back as well as this cause me to rock my hips forward giving me the tingles in twig and berry's.
Like other have pointed out your knee problem is probably more from spinning out on the single and braking with the pedals on the fixie.