Fins

I know they just test marketed all these various fins but I still have a question. Whenever I use fins I get bad leg craps and pain in the front/side of my shins and foot pain. Has anyone ever experienced this? And tried a different fin? a shorter one. Mine seem to be a medium lenght. Any recommendations? Ankle Stretches (GoSwim.tv)

I know they just test marketed all these various fins but I still have a question. Whenever I use fins I get bad leg craps and pain in the front/side of my shins and foot pain. Has anyone ever experienced this? And tried a different fin? a shorter one. Mine seem to be a medium lenght. Any recommendations? Ankle Stretches (GoSwim.tv)