Aggravating left knee is hurting. Wonder if I pulled a hamstring. I'll Google "hamstring" to see if I did.
What did Google say about the hamstring? 
Inconclusive. It's probably too late to see a doctor since it happened Sunday night. Don't laugh, but I hurt it trying to sit in the computer chair, the one I couldn't get into and had to do a hoppy thing to get into it? Well, I hopped and the leg popped.