now that this is off topic, i'll throw in my two cents (or more
)
glucosamine, chondroitin, and MSM are very good to take. they definitely help lubricate the joints. however, the best form to take these is liquid, so you might look into that (it tastes awful, but it does work)
upping your protein and working the surrounding muscles is also good. tigger was right- squats are good, leg lifts are also good (ankle weights add resistance and are good when you're ready for it)
honestly, the best thing to do is to lose that 20 lbs aerobically. i'm not telling you to go run marathons, but whatever aerobics you can deal with (running is just the obvious one, but jumping rope, stationary bike, elliptical, whatever you can handle) is going to make the most difference.
http://www.hopkins-arthritis.som.jhmi.edu/mngmnt/osteoandweight.html#joint