It starts with a little stiffness in the left knee. The pains get worse and you are having trouble doing your morning jog or even climbing the stairs. Your medical examination shows you have arthritis. "Almost everyone over the age of 50 has signs of it, if you look hard enough. Arthritis is the number one cause of movement limitation and probably the leading cause of disability if you consider that people often become sedentary due to the associated aches and pain," says Jason Theodosakis, author of "The Arthritis Cure".