Knee osteoarthritis (OA) is a debilitating disease that affects an estimated 20 million Americans, and contributes significantly to functional limitations and disability. Normal activities of daily living, such as climbing stairs, becomes more and more burdening for those who suffer from knee OA. Surprisingly, very few studies have examined changes in overall gait characteristics and lower extremity joint kinematics during stair climbing in subjects suffering from knee OA. Therefore, the purposes of this study were to (1) compare overall temporal-spatial gait characteristics during stair ascent and descent between knee OA subjects and matched healthy controls, and (2) compare lower extremity joint kinematics during stair ascent and descent between knee OA subjects and matched healthy controls. Twenty subjects with knee OA and 20 matched controls performed 5 walking trials up and down a staircase while their motion was captured three-dimensionally using an optical video motion capture system. The results showed that knee OA subjects demonstrate deficits in overall walking gait characteristics when ascending and descending stairs. Further, knee OA subjects experience peak hip flexion angle during support later in the gait cycle compared to healthy subjects during stair ascent. Knee OA subjects also demonstrated smaller average knee flexion, but larger hip and ankle flexion angles at foot strike during stair ascent compared to healthy subjects. These findings elucidate that knee OA subjects not only experience alterations in knee joint kinematics during stair climbing, but also develop kinematic alterations at the hip and ankle to compensate for the knee joint pathology they suffer from.