Thanks for query,
The problem of standing straight is due to your weight only as knee joint cannot take weight of your body.
You should loose weight that is the only motto in your life.
Just avoid sugar from your food.
Take leafy vegetables 70% in your diet.The other 10% is of curd & rest of 20% contains carbohydrate
Drink adequate water to hydrate your self.
Take small frequent mills just to satisfy yourself.
Light exercise of hands will burn some more calorie.