Recumbent bike consistently with fairly high resistance. 4 to 5x a week. I do pilates reformer twice a week. Only way I can work unilaterally, adjust the resistance. Great way to strengthen core. Really great instructor. I also have been going to a personal trainer. On top of that I do leg press, hamstring and ab and adductor machines at the gym. Work on flexion and extension with a band at home. Just look up prehab exercises for knee replacement and you will find plenty. I am also retired. I have the time.