Have you considered Tai Chi? If you can find a Tai Chi teacher around, give it a shot. Make 'em aware of your situation (the surgery, etc.) so they'll make any needed adjustments. Tai Chi is good for health and healing (e.g. injury/illness) with a martial arts base to it. Even once or twice a week is good, allowing you to practice those basics by yourself. It will feel a little different than many of the Japanese and Korean martial arts.