What retro said. If you can't bend your knee enough, the problem is at the top of the pedal circle. You'll have to make the circle smaller, otherwise if you simply move the top of the circle away from you, you won't be able to reach the bottom of the circle. This is true no matter whether you're riding uprights or recumbents. You can either get shorter cranks, which can come as small as 135mm I think, or you can get crank shorteners (cheaper alternative while you test the concept.)