Osteoarthritis results from an imbalance between the breakdown and repair of articular cartilage in any joint and occurs as a result of multiple risk factors, including trauma, overuse, and genetic pre- disposition. Osteoarthritis (of any joint) was the primary diagnosis that led to 11.3 million ambulatory care visits in 2009.1 The Centers for Disease Control report that one in two individuals may develop symp- toms of osteoarthritis in at least one knee by age 85 years.