I woke up this morning with a really bad pain on the left side of my knee cap. It only hurts when I put pressure on it or when I bend my leg back (Heel towards back). Do you think it's a pulled muscle, or something mroe serious. I took a nap and after waking up it was even more stiff. I haven't done anything out of the ordinary lately, nothing that would cause the pain. Should I see a doctor? Do you know anything that might help it?