Hi,
I think the simple answer is to use weights and rubber band resistance to work on all the muscle groups you can in ways that do not cause you knee pains and added problems. There are also a lot of gymnastic exercises (like push-ups) that you can do without any equipment at all. If you have no experience with training or training programs, you may want to find a professional coach to design a program for you.
For your knee problem I am not promising anything, but I know of many people that have had amazing results from drinking alkaline water. You can find all the necessary free information by Clicking Here
Good Luck from Knut