Very sensible advice, tangoteen.
running is best for aerobic fitness and it makes you feel great. Run on grass - proper shoes - no more than 5 miles at a time.
Wall sits are brill for strengthening knees. I would personally avoid squats. Lunges are good.
The main thing is to follow a regime that can be part of your life. Once a week for 4 weeks is no use - though probably better than nothing.