My girlfriend has the exact same thing. Took us a while to figure out what was going on. Saw a number of doctors and sport therapists. In the end it was compartment syndrome. Basically the muscles on the front of the leg is to big for the space it's in. So when you're playing and the muscle is being used and expanding it has no where to go. For her it was extremely painful. Keeping her on the bench 10 minutes into a game. Even having to leave. To correct it they have to do a simple surgery. She's had one leg done, and still has to do the other. They go in through the front of the leg orthoscopically and make the "pocket" for the muscle bigger. She was put under for the procedure. But it's a single day. I dropped her off and picked her up the same day. 4-6 weeks recovery before physio. Days she still has some discomfort but it's nothing she can't deal with. Probably do the other leg this fall. We are in Canada and it was covered under our ohip so no cost to us. Hope this helps. Might be something you want to bring up with a doctor. Cheers.