http://arthritis.about.com/od/kneetr...supplement.htm

There is stuff that can be injected into the knees of someone with osteo. Have a look at that link. As long as it lasts and doesn't have to be repeated a lot, it might really help.

More:

A first line of simple treatment - acetaminophen (Tylenol) is as effective and has less side effects than other non-steroidal anti-inflammatory drugs (NSAIDS) such as ibuprofen, naproxen, or aspirin. Glucosamine-chondroitin sulfate may be prescribed by your doctor. This medication, when taken over a period of months, may reduce pain and symptoms by restoring or replenishing nutrition to diseased cartilage cells. It tends to be more effective in earlier stages of OA. The dosage and combination of each ingredient is an important aspect of the therapy, as not all preparations and brands are the same.
There are also partial knee replacements:
http://en.wikipedia.org/wiki/Partial_knee_replacement