Participants will be randomly assigned to 1 of 2 treatment groups. Both groups do the same exercise program 3 times a week for 12 weeks on nonconsecutive days. The only difference is that one group will perform the exercises with small resting periods between exercises as normally done in clinical practice. The other group will have two long rests of 45 minutes during the exercise training session. Before and after the exercise programs, participants will undergo a series of assessments including gait analysis, MRI imaging of knees, tests of muscle strength and physical performance. Questionnaires will be completed. Blood and synovial fluid will be collected as part of this study.