60 patients scheduled for total knee arthroplasty were randomized to postoperative usual care with or without the addition of an app-based, feedback-controlled muscle activation trainer (GenuSport Knietrainer). Patients allocated to the trainer group was prescribed 3-5 sessions of use of the trainer during hospitalization. Results demonstrated significantly greater active knee range of motion and lower pain on movement at discharge in the group allocated to trainer use compared to those who were not given the trainer. Length of hospital stay averaged 6.6 days (+/-1) and 6.9 days (+/-1) in the trainer and control groups, respectively.