Go back to some basics and see if you are twisting your body to face forward. I used to find i'd tweak my front knee/leg by facing forward and tucking my back leg in. Had some weird angles going on that my leg didn't like
I really suggest having someone film you riding. You can learn a lot from watching yourself ride. You may be doing some things you have no clue that you're actually doing.
"People say that marijuana smoking is going to get in the way of my career. I say to them that on the contrary, my fighting career is getting in the way of my marijuana smoking." -Nick Diaz