Severe OA of the knees

I'm living with Severe OA of both knees for about 6 years and getting progressively worse. I've taken steroid shots e and drainage every 3 months or so and really doesn't do mush for pain . I'm also overweight and can't seem to lose weight fast because it's too painful to do exercises standing up or walking .I need to lose 120 pounds the doctors said to get the weight off my knees , even 25 pounds would make a difference. Can anyone in similiar situation let me know how they have lost weight. I have no access to a pool . Only have stationary bike but can't do but 10-15 mins on it.I have dvd's of chair dancing that I do , but still need another way . Would appreciate any tips. Thank You .My name is Linda