The resumption of a physical activity is very important
Contrary to the generally accepted ideas, the sport makes little lose weight (it would be necessary to make sport on a level of drive to the Olympic Games to lose much weight), but it enables you to stabilize your weight loss.
The first month : progressive resumption of the physical activity (walking).
I disadvise the bathes, especially in swimming pool (because of chlorine), which can support a bad cicatrization of the skin.
After the first month : you can take again any sport.
The simplest activity is walking : find moments to walk each day (descend from public transport one or two stations before the arrival, park a few kilometres from your place of work, take the staircase when you have few stages to go up).
Buy a podometer (small device which counts the steps, which is fixed at the belt) in a sport shop. Try to walk 10 000 to 12 000 steps per day.
This physical renewal of activity must be very progressive.
More you will lose weight, more it will seem easy to you, profit in to increase the duration of your physical activity.
If you have osteoarthritis on the level of the knees and hips, go to swimming pool 2 or 3 times per week.