Osteoarthritis is the loss of the cartilage on the end of the bone. It's not the accumulation of debris necessarily, although that can be a secondary thing, but it's the loss of the smooth surface on the end of the bone. Well, that's again a loaded question in that regards because we really don't know (who is at risk for developing osteoarthritis). People who have a genetic predisposition, maybe a family history. People that are overweight. People that overuse and are overweight, so it's kind of a combination of multifactorial things. People that have had a prior injury to their knee, whether it be an ACL injury in high school.