I have osteoarthritis in both knees, so I know how it is. Also, I've seen a lot of threads covering this topic, so you may want to do a search to see what others have posted. My doctor has limited me to biking, swimming, and elliptical machine. No walking, jogging, running, dancing, etc. (Although I do walk/speed walk. I totally cheat.
Hate to tell you this, but you may have to give up the 30DS. It may be too high-impact for your knees. Or, alter the moves so they are not so hard on your knees. And, I second the suggestion of seeing a doctor. They can even send you to PT who will help you build up your knee strength, and show you safe exercises to do without doing further harm. Best of luck!