In each of the first three groups, we will determine whether people assigned to strength training have lower pain scores and/or slower progression of radiographic changes of OA over 30 months than controls who perform nonstrengthening exercises (i.e., range-of-motion exercises). We are including the fourth group to determine whether those with OA (groups 1 & 2) exhibit the same response to strength training as healthy elderly people, and whether those with knee pain (groups 1 & 3) have the same response to training as those without joint pain. We will also prospectively monitor changes in body composition and bone mass, quality of life, and symptoms of depression.