Out of Shape

I am sitting here contemplating the fact that I need to exercise and get back in shape. Believe it or not, I played sports year round until I graduated from high school (which seems like a very long time ago at this point....1995). I played soccer which demanded me to be in good shape; I wrestled which made me be in great shape; and I played church softball which kept me going until soccer started back. However, I am no where close to that kind of shape. Now, I'm in a different shape (which you do not need to comment or amen or anything). But the Lord has been convicting me for years now about how I eat and how I take care of my body. I used to publicly claim that I was going to do this or that and then fail at my attempts to get back into shape. Then I quit sharing and hoped to "surprise" people when I got in shape. Neither of those have worked. So, here I am, out of shape, still convicted, and needing a change. So this is a post asking for advice on how to get in shape. I'd love to hear your thoughts. Where do I begin? Keep in mind, I'm heavy enough right now that running hurts my knees and the ankle I broke a few years ago. I may have to lose about 20-30 pounds before I can run. What are your suggestions?