Creeky

Ever since I helped my brother move over the forth of July weekend, I have had trouble with my knee. This is something new for me because I've never really had aches and pains before. I went to my spin class last night and while it didn't bother me during class, when I did a stretch afterward it didn't feel right. It hurt all night and now unless I keep it bent its pretty painful. What the heck? I'm only 30. Why am I breaking?