I feel like you may have a few additional problems with the fake knee and the clipless pedals. I'm not sure how your range of motion is, but it requires a rotation outward with your ankle (and some knee twist) to get them to unclip. I'd say half clips like FrenchFit said. You won't get the efficiency of clips/straps or clipless, but it'll be better than your foot sliding off. It may help stretch out your knee a little too.