I'm sorry to hear that, Are you attempting to diet? I know for me I feel immeasurably more healthy at 95 kg than I did at 115kg and that will certainly help coronary risk too. I know its very hard to do especially when its hard to exercise. Have you considered going to your local swimming pool? its very easy on the joints and even gentle movement in the water burns quite a few calories, not just because of the exercise but because your body has to work to keep warm. I can't go at present because of my recent accident, but its certainly my first choice of exercise and much less dangerous than walking it seems !