Juvenile idiopathic arthritis (JIA) is one of the most common chronic illnesses in children, with recent data suggesting that 1 to 4 in 1000 Canadian children and youth cope with the condition. Many JIA children will enter adulthood with permanent joint damage5. In parallel, a significant number are affected by deficits of muscle function. In addition to the impact on physical function, muscles play an important role in maintaining joint health. The overall aim of this proposal is to evaluate a novel therapeutic intervention - whole body vibration (WBV) - for its ability to improve muscle function and the biomechanics of lower extremity joints in JIA in order to prevent joint degeneration.