Osteoarthritis occurs when cartilage (the gristle that lines the ends of the bones) is damaged. It is the most common form of hip arthritis and is responsible for more than 90 percent of hip replacements. Recently, subtle deformities of the hip have been linked to hip osteoarthritis, and it is now believed that these deformities, combined with certain types of physical activities, such as hockey, soccer and bicycling, are one of the major causes of damage to the hip. Since the deformities have been observed in young adults, it may be possible to detect and treat osteoarthritis at an earlier stage, or prevent its development. Dr. Chuck Ratzlaff’s research will demonstrate how physical activity and one or more subtle deformities of the hip can cause cartilage damage and eventually osteoarthritis. He will determine the frequency of deformities in the Caucasian population in comparison to the Chinese population, which is thought to have a lower frequency of osteoarthritis. He will also determine how physical activity over one’s lifetime contributes to osteoarthritis. For this study, participants with and without hip pain from both Caucasian and Chinese populations will attend a two-hour assessment session consisting of a physical examination, a hip x-ray, and a questionnaire on physical activity. He will use new magnetic resonance imaging (MRI) techniques to see how the physical motion and the deformity combine to damage cartilage. This research program will generate the new knowledge needed for major breakthroughs in the prevention, detection and treatment of hip osteoarthritis. Given an aging population and the increased prevalence of chronic diseases in Canada, physical activity is an important intervention for health. Knowledge of how to modify and perform physical activities, and identification of susceptible individuals, will lead to inexpensive and practical recommendations that maximize the benefits of physical activity without increasing the risks of joint disease. It may also lead to identification of a subset of people that will benefit from minor hip surgery to correct the subtle deformity, thus preventing the later development of hip osteoarthritis and its associated burden of suffering and other costs to the individual and society.