I am 33 weeks and my knees just started hurting me. I'm pretty sure its from the extra weight for me anyways. Pregnant ladies tend to have joint pain in different places I have read. Good luck.
I had this just last week. I was asleep and woke up with achey joints but particularly in my left knee, so bad I couldn't really walk and forced myself to rest all day. The next day it was gone as if it never happened. I massaged castor oil on my joints and that seems to help. I'm 24wks today, hoping no crazy symptoms appear this week, lol! Hope you feel better soon!