Ditto needs some fun in her life

[vicky2200]

Background information: Ditto is a nearly 5 year old spayed female. Last summer, I posted on here about being concerned about her sudden decrease in activity and limp. It turned out that she hurt her knee. Nothing too serious, but enough to make her not want to do much for a long time. She gained 9 lbs during this time. Before this, she loved to play fetch. We would play for hours several times a week when weather permitted. She also enjoyed going on runs with me. We worked up to 5 miles. The vet gave us pain medication for awhile and she seems fine now, but we are reluctant to let her play fetch or go on runs since her knee will likely never be the same.

So Ditto pretty much does nothing all day. I feel really bad for her. Now, it is still the winter (although the current weather disagrees) so normally we wouldn't be doing much anyway. I need ideas of stuff I can do with her that wont put (much) stress on her knee. I plan on taking her to the lake in the summer to play fetch in the water, but she isn't the greatest swimmer so I don't throw it far. This isn't something I would be able to do all the time, but I intend on trying to do it at least a few times a month when the weather improves. I am also going to try jogging her, but only 1 mile. If she shows any sign of pain, we will stop. This still doesn't seem like enough. She LOVED fetch. She has lost a little bit of the 9lbs and the vet says she isn't over weight, but I would prefer her to lose at least 4 more. Any ideas? I don't have money, so anything (even cheap things) that costs money is out of the question.