New cause of osteoarthritis discovered

Osteoarthritis is driven by low-grade inflammation, which is at odds with the prevailing view it is brought on by joint wear and tear, U.S. researchers say. Dr. William Robinson of Stanford University School of Medicine said the finding offers hope that by targeting the inflammatory processes that occur early on in the development of osteoarthritis -- well before it progresses to the point where symptoms appear -- the condition might someday be preventable. "It's a paradigm change," Robinson, the senior author of the study, said in a statement. "People in the field predominantly view osteoarthritis as a matter of simple wear and tear, like tires gradually wearing out on a car." It also is commonly associated with blowouts, such as a tear in the meniscus -- a cartilage-rich, crescent-shaped pad that serves as a shock-absorber in joints -- or some other traumatic damage to a joint, Robinson said. It has long been known that osteoarthritic joint tissues host a heightened number of migratory inflammatory cells and of some of the substances these cells secrete -- "not nearly as much as in the case of rheumatoid arthritis, which is clearly an autoimmune disease, but enough to make us wonder if inflammation is also a major player in osteoarthritis as well," Robinson said. Robinson's team's said the increased numbers of certain specialized inflammatory proteins early in the progress of osteoarthritis, before it becomes symptomatic, suggested that inflammation might be a driver, rather than a secondary consequence, of the disease. The finding was published in the journal Nature Medicine.