Cannabinoids: new friends in bone fracture and in joint disease prevention?

n recent years the endocannabinoid system (ES) has been recognized to play an important role in the regulation of several physiological processes, including pain perception, appetite control, and motor function development. This system has recently been recognized to be present in bone and joint tissues, playing a role in the regulation of bone and joint physiology. The ES seems to play its role mainly by acting on its receptors and thanks to the demonstrated ability of bone cells to synthesize the principal endocannabinoids (i.e., anandamide and 2-arachidonoylglycerol), which can act on bone remodeling and metabolism. Cannabinoids have also been shown to be produced within synovial tissues, and recent studies have shown that cannabinoid receptor ligands are effective in the treatment of inflammatory arthritis. In recent years synthetic endocannabinoid-like compounds and phytocannabinoids, which are the principal components of Cannabis sativa, have also started to be studied as molecules that could play a role not only in bone physiology, but also in the pathogenesis of osteoporosis, the most common bone disease, and in the inflammatory processes underlying osteoarthritis. Accumulating evidence that cannabinoids and their receptors play an important role in bone metabolism and in the regulation of the immune response is now starting to show us the true future therapeutic potential of cannabinoids, and of the phytocannabinoids contained in Cannabis sativa, in the treatment of bone loss and joint diseases. Here we summarize the role of the cannabinoids and their receptors in bone metabolism, osteoporosis, and joint disease.