S-Adenosylmethionine (SAMe), a physiologic compound that ranks with ATP as a pivotal molecule in biology, offers physicians an innovative approach to the treatment of osteoarthritis. Experimental investigations suggest that the administration of SAMe exerts analgesic and antiphlogistic activities and stimulates the synthesis of proteoglycans by articular chondrocytes with minimal or absent side effects on the gastrointestinal tract and other organs. The results of extensive clinical trials, which have enrolled about 22,000 patients with osteoarthritis in the last five years, support the clinical effectiveness and the optimal tolerability of SAMe administration. The intensity of therapeutic activity of SAMe against osteoarthritis is similar to that exerted by nonsteroidal anti-inflammatory drugs, but its tolerability is higher. Based on these findings, SAMe is proposed as the prototype of a new class of safe drugs for the treatment of osteoarthritis.