Trying to move on - struggling with side effects of radiotherapy. What exercises can I do to help my knees?

Hello everyone. My name is Chrissy. I am 4 years in remission from cervical cancer. My problems are all to do with side effects of radiation. I feel as if I have suffered more with this. 

 I won't go right into it but basically there was blood in my poo, had all tests but everything normal. Apparently the blood was because of radiation.

What I need now is some advice on getting back on my feet once again. Is there anyone who could furnish me with some exercises for my weak and aching knees. My gp approached our local physio dept to see if they would help but they said no as I had already had physio.

I  would be grateful for any advice. 

THANKS, CHRISTINE.