You might drive again as soon as 3 weeks after your surgery. But most people need 4-6 weeks before they can bend their knee to get in and out of the car.
In 3-6 weeks, you could shop for groceries, get up from a chair, and do other things that were difficult before the surgery. Just remember that you might not be 100% pain-free. Let you doctor know about any pain that bothers you.