Although total knee replacement (TKR) improves pain in numerous patients, it does not resolve many of the substantial functional limitations and physical inactivity that existed for a long time prior to the surgery. Exercise is an intervention that could improve these long-term limitations. To promote these improvements, exercise should be implemented at later stage post TKR when patients can tolerate doses of exercise sufficiently high to promote substantial changes. To date, we just don't have enough good research to tell us which type of exercise works best for which patients and under which circumstances at later stage post TKR. This research study will provide evidence for recommended interventions during the later stage post TKR. The specific research questions are: (1) How do group exercise in the community and individual exercise in rehabilitation clinic compare with usual medical care on physical function and activity outcomes? (2) Who are the patients most likely to respond to each exercise intervention? (3) Are the approaches safe?