Sore knees :(

It might be from having tiny muscle cramps overnight. I used to get massive leg cramps at night with each pregnancy until I discovered the miracle of brocolli!!!! I eat brocoli with almost every dinner and make a couple of pieces extra which I put in the fridge and eat right before going to bed. There is something in brocoli that prevents muscle cramps and I have not had them since.
You might want to think about those knee support things during the day too, as the extra weight of pregnancy might be tiring out your knee joints.
Next time you see your midwife you should definatley tell him/her about it. Pains in your legs can be a sign of DVT which is common in pregnancy as our blood thickens with the extra hormones.
Good luck! I hope it clears up for you!