Runs in my family too, almost everyone has had some sort of surgery, and I was wondering the same thing, I have had my ACL repaired and its been flaring up pretty regularly now that I'm further along. But I don't think its something you'd need surgery for.
Definitely normal in pregnancy, especially with you being this far along. It's a mix of extra baby weight and pressure of the baby in the uterus. Baby's position can actually affect some of your nerves in your body. Don't worry! Make sure you're taking breaks though.