This is a comparative effectiveness study, designed as a 3-group single-blind randomized clinical trial. Two hundred forty older adults who underwent TKR at least 2 months prior and are otherwise eligible will be randomized into one of three treatment approaches: 1) clinic-based individual outpatient rehabilitative exercise; 2) community-based group exercise classes; or 3) usual medical care. Subjects will be treated for 3 months. Data will be collected before intervention, after intervention (3 months), and 6 months after randomization. Physical function is a primary outcome and will be assessed by the Western Ontario and McMaster Universities Arthritis Index and a battery of performance-based tests germane to patients post TKR that includes ability to walk, manage stairs, lift from the floor and the chair, and one-leg balance. We will also use an accelerometer-based monitor that provides a real-time measure of physical activity during normal daily living and is able to accurately capture most levels of activity. Linear mixed models will be fitted to compare the changes in outcome across groups. Logistic regression will identify patient characteristics that predict functional recovery in the exercise groups. Survival analysis and instrumental variable methods will be used to compare attrition, adherence and adverse events between groups.