What are good exercises with bad knees

I searched the forum and didn't see anything on this and if I missed it I am sorry. I am about 2 years away from knee replacement and I am overweight. My doctor's all tell me to lose weight and exercise but both knees are bad and the ortho doc said do not walk or even get on a treadmill because of the knees. Does anyone have any suggestions on the types of exercise I can do to help sweat and get fit?

Thanks in advance.

Bryant Dodd

What are good exercises with bad knees