You are right, it can be very difficult fighting the battle with weight when you also have an underlying thyroid problem. First you should ensure that your doctor has your thyroid hormone level optimized. This will help with stabilizing metabolism rates, and also likely with your energy level.
In regard to treating Type 2 diabetes: the medications we have work on reducing the blood sugar numbers which is very important because that is what does the damage. They are not aimed at curing diabetes per se, this is true, but by lowering the blood sugars they limit the damage the disease can do. If you still have enough insulin production of your own, and the main problem is insulin resistance(your body isn't responding to your insulin for a number of reasons), then weight loss is your best solution in trying to rid yourself of diabetes. Your knee problem unfortunately is not helping--perhaps there is a nearby pool that you can use for swimming amd exercise, and will also take pressure off your knee.
I am a big believer that the proper diet will always help with weight loss. I do not prescribe to a specific diet in terms of low carb etc--I simply suggest to people that they cut back on everything except the greens. An easy way is to start by putting back 1/3 of the food you dish out on a plate, and drink water as much as possible instead of other drinks. Monitor the amount of processed food you eat and try to stay with 1 person-serving sizes(much of our restaurant food and processed foods are more than 1 serving size when you read the label).
If you can, try to speak with a dietician at a local health department. You can also find some helpful food tips on the American diabetes association website.
Hang in there and give it your best shot. Small increases in exercise coupled with reductions in what you eat will all start adding up to some weight loss.
I am not the doctor, I am sure she will answer u by Monday evening. First my heart goes out to u for the struggle u are facing. I have the same trio that u have all except the Thyroid. I feel one health issue lead to the next.. I don't understand this either, I get put on diabetic meds' and not long after came the high BP and then came the rising cholestrol. Sometimes I think I was better off on my own. Every diabetic out there at some time ends up with this trio and I have my own feeling on it. So to help u get better, what kind of diet do u eat? And what med's are u on? I know the Dr would like to know bothof those question to help answer your questions. Being a diabetic with the trio u need to get that weight off and u will get better. First find some information on LOW CARB DIETS or a diet which limits the starchy carbs and replaces them with the high fiber grains. Get the white rice, the white pasta's out of your diet. The white potatoes also. And cut ur portins to a normal portion. Read labels, and regular sodas, fruit juices are loaded with sugar. And Butcher, exercise even in the low side for just 30 min a day, walk slowly, park your car farther from the store and go slowly. Stretch your arms over your head and bend a little to the side, or even get some soup cans or veggie cans and use them like weights. Lock your arms around your head and turn thm slowly to one side and hold and then to the other side and hold. when u are sitting stretch your legs point your toes to the wall and realx them and bring them back toward u. A few mins a day and just a little effort, and your body will thank u. I know for sure if u change your diet and look up the information it will help you to loose the weight. Check out Dr. Atkins diet. Go to www.Lowcarbdiets. There are forums and so much help. I hope I helped a little