MSM is methylsulfonylmethane. It is an organosulfur compound with the formula (CH₃)₂SO₂. It is also known by several other names including DMSO₂, methyl sulfone, and dimethyl sulfone.

Research performed at the University of California at San Diego looked at the effect MSM has on cartilage. It was published in the Osteoarthritis and Cartilage Journal (available online December 27, 2007). This was an “in vitro” study, meaning that the researchers looked at cartilage that was outside of the body. They were concerned with cytokines, which are chemicals produced during inflammation and associated with damage done to joints. MSM acted to reduce the effect of the cytokines and act to protect the cartilage. According to the head of the research team, David Amiel, “It suggests that MSM acts as a barrier, shielding cartilage in early stages of osteoarthritis from further degeneration from inflammatory cytokines and cartilage degrading enzymes.”