Glucosamine and Chondroitin Sulfate are part of the elements of your joint cartilage. When taken orally for arthritis, and especially with Magnesium, they provide relief equal to anti-inflammatory drugs, as documented in recent studies. How it works is not clearly known. It is less costly than drugs and has little or no side effects. I have been recommending it to my patients for over 5 years with good results.