When I do a round off I cross my legs?

So here what I do, I run, I hurdle, and after my hurdle I land my foot and my right foot crosses over my left, then I do my round off. How do I stop this, My foot is suppose to land in front of my left foot, not cross over it. I have patella femoral syndrome which means my knees go in. Is this the cause of it? Please help. How to I stop this.