Ballet Dancing Often Causes Osteoarthritis     Ballet Dancing is considered a beautiful art form and the dancers are applauded and revered throughout the world. Physicians who take care of ballet dancers, however, realize that they are extremely exceptional athletes. Dance medicine has actually become a subspecialty of sports medicine in some medical centers. Their types of activities are much different from the usual athletes that we treat.     Ballet dancers pay a high price for the activities that they perform.     Study of a group of dancers from the National Ballet of Canada found problems in almost every dancer, including early signs of arthritis, fluid in the ankle and other joints, inflammation in the tendons and ligaments of the foot and ankle.     What makes matters even worse is that they often begin their training long before skeletal maturity, causing even more problems. Throughout their career they usually take very little time off from training and rehearsing, even when they are not performing. Their dance activities often take several hours a day.     Almost all of the dancers perform with pain much of the time.     In addition to arthritis of the ankle and joints of the feet, which is a more long term problem, dancers experience stress fractures, deformities of the toes, bunion problems, and tendonitis.     A lifetime of painful feet and ankles often awaits them when they can no longer perform.     Medical attempts at suggestions to change training routines or modify foot wear worn by ballerinas have been completely unsuccessful, unfortunately.