Ladyjane: No offense taken at all!!
Honestly after I wrote that and I started watching Sophie and thinking about it, She is kind of a drama queen. Lol.
I am pretty sure it wasn't her knee that caused the yelping. She had been chewing a bone and had gone into the kitchen to get something to eat. Nothing has happened since then, so she may have swallowed something wrong or hurt a tooth. She is just fine now so I will just ask my vet about the knee next time we go which is soon for boosters. From what I am seeing in the posts, this seems to be a common problem with Yorkies.
I just don't want her to be in pain...
Vinniedoggy: I have a friend who stays with me and she told me that when Sophie sees me leave, she lays by the door and sighs and whimpers. That is the only reason I know she does it. I hate that she does that, it makes me feel so bad. That is a really good idea about leaving clothing for her. I guess the smell will calm her.
Thank you everyone for your advice and well wishes, it is so nice to find dog lovers like me!!