I hadn't used it until a few weeks ago. Had inflammation around the knee/hamstring that came without warning, and I couldn't straighten my leg. Ice/ibuprofen did little to the swelling for 3 days. I bought liquid DMSO and applied it that night. The next morning it was much better, and I could bike and run a bit. The next day I was totally better, and no subsequent swelling.
You have to clean it completely, with something like Hibiclens preferably. Can be expensive, but worth it I think.