1) A majority of people afflicted with osteoarthritis (OA) of the knee are elderly and many have their OA exacerbated by obesity. 2) Healthy older adults exhibit gait patterns that differ from a healthy, younger cohort. These differences include a slower walking velocity, slower cadence, shorter step length, reduced hip and knee range of motion, and greater stride width, vertical oscillation, and lateral sway of the head. 3) Subjects afflicted with knee OA have decreased knee range of motion and knee angular velocity, increased loading rate on the less affected leg, and a compensatory increase in hip angular velocity when compared with age matched healthy subjects. 4) Obesity, which is strongly associated with knee OA, increases rearfoot motion during walking and causes the forefoot to abduct significantly more than in normal weight individuals.