Start small with your eating habits. A good first step that I recommend to a lot of people is to start counting calories. Once you start to understand portion size and content a little better (maybe after 2 weeks or so), watch your carb/protein/fat ratios a little more closely - mainly you just want to make sure you are getting enough protein and not too much fat. Then start cutting all the bad carbs (white bread, sugar, cookies, ect) and replacing that with good carbs (veggies, fruit, whole grain/wheat bread). These are a few steps that should help get you back on track.
As far as the exercise goes, if you have hip, ankle, and foot problems, maybe you should be looking into a different type of exercise such as swimming or even ellipticals.
Good luck!!