Participants in the intervention group coud only view the rehabilitation content that needs to be carried out at the current phase every day and confirm whether to execute it on the application. Participants could communicate with therapists on the mobile phone application by sending text, voice, images, and videos throughout the entire experiment.

Participants in the intervention group received detailed education and rehabilitation program on the mobile phone application including text, photos, and videos. On the first day of enrollment, the doctor inform the participants of the importance of rehabilitation and how to use the mobile phone application. The postoperative rehabilitation protocol includes four phases: Phase 1 (0-2 weeks), Phase 2 (3-4 weeks), Phase 3 (5-8 weeks), Phase 4 (9-12 weeks), and Phase 5 (after 13 weeks).

Participants in the control group could only receive a graphic and textual minimal postoperative rehabilitation plan on the mobile phone application. However, the participants was not informed the frequency and intensity of the rehabilitation items. They could not communicate with therapists online. Participants in the control group was expected to exercise unsupervised postoperatively.

At the 2, 4, 8, 12, and 24 weeks after ACLR, all participants went to the outpatient clinic for follow-up by physiotherapist to provide face-to-face guidance for exercise methods. Physiotherapist would clarify the content of the rehabilitation plan if any doubt, but will not provide information extending the prearranged scope.

The whole program is constituted of preoperative education and postoperative rehabilitation (in hospital and out of hospital). All the participants received the same preoperative education through the mobile phone application and oral communication. Participants in the intervention group get the multicomponent supervised tele-rehabilitation, while participants in the control group get the home-based self-rehabilitation. All the postoperative rehabilitation programs are presented and executed through the mobile phone application.

In the first 3 months after ACLR, the achievement of acceptable knee active extension and flexion was regarded as what matters most for a successful recovery. A good knee active ROM could guarantee an expectedly continue improvement.

The active and passive ROM of the affected side knee

The postoperative pain was measured with VAS. The VAS scale ranges from 0 to 10 points, 0 points represent no pain, while 10 points represent the worst imaginable pain. A higher VAS score mean a worse outcome.