Hi. I am a cheerleader and I really bad pain in my left knee. It hurts when I sit for longer than 30 minutes and it s really a pain as a student in college. Recently, I pulled a muscle below my left thigh, but even before that this pain has been bothering me. The pain sometimes travels to my shin and to my hip flexor as well. Whenever I stretch my left leg (splits, lunges, etc.), I just get terrible pain in my left knee. What is this?