Mobile-Based Telerehabilitation With Sensors for Adherence and Efficacy in Chronic Patellofemoral Pain: A Randomized Controlled Trial

The inestigators conducted a forward-looking, single-center pilot study with a follow-up period of 8 weeks. The study recruited 174 patients diagnosed with patellofemoral pain (PFP) by a professional sports physician at the Department of Sports Medicine, Peking University Third Hospital, between June and August 2024. The study adhered to the principles of the Declaration of Helsinki and was approved by the Research Ethics Committee of Peking University Third Hospital. Although this is a pilot study, the inestigators strictly followed the CONSORT guidelines. All participants signed an informed consent form and completed home rehabilitation interventions.

Inclusion and Exclusion Criteria During the trial, an investigator not involved in the study used an electronically generated random sequence to assign patients to three groups. Two professional physical therapists (N.C and S.R) were responsible for assessing and supervising the accuracy of the project and were unaware of the grouping details.

Interventions After randomization, participants received a package containing two wearable motion sensors, a charger, resistance bands, and a manual. Additionally, the rehabilitation software provided lectures and Q&A sessions related to the condition, accessible via Android or iOS platforms. All data collected by the sensors were strictly encrypted to protect patient information and privacy. Each participant was assigned a therapist for home rehabilitation support, and a follow-up function via the software or telephone was used to remind patients who missed three remote rehabilitation sessions.

Before starting home rehabilitation, patients attended a briefing at the hospital. Participants were divided into three groups: Group 1 received 1 face-to-face remote rehabilitation tutorial (OST), Group 2 received 3 face-to-face remote rehabilitation tutorials (TST), and Group 3 received 6 face-to-face remote rehabilitation tutorials (SST). Each session lasted 40 minutes and was conducted three times a week (on Tuesday, Thursday, and Saturday). Following the briefing, patients performed home remote rehabilitation training on the same day, with each session lasting 40 minutes. The remote rehabilitation program included muscle strengthening, flexibility stretching, and movement quality training.

Primary Outcomes. The primary outcome was device-recorded training adherence, defined as cumulative total training time (hours) and mean weekly training time (hours/week) over the first 6 weeks of independent home-based telerehabilitation. Data recording commenced immediately after each participant completed his or her final face-to-face tutorial, thereby isolating adherence to the unsupervised home program. Because the three groups differed in the number of tutorials received, the calendar start date of the 6-week recording window varied: OST participants began the recording window after session 1; TST participants after session 3; and SST participants after session 6. The 6-week duration of the window was identical across groups.

Secondary Outcomes. Self-reported adherence was measured using the Exercise Adherence Rating Scale (EARS) at week 6 (i.e., 6 weeks after the participant completed their final face-to-face tutorial). The EARS comprises Section A (6 items assessing adherence to prescribed home exercise) and Section B (10 items exploring barriers to adherence). Items are rated on a 5-point Likert scale (0 = "strongly disagree" to 4 = "strongly agree"), with positively phrased items reverse scored such that higher scores indicate better adherence. The EARS has demonstrated good reliability (Cronbach α = .85) and construct validity. (Multimedia Appendix 3). Secondary engagement metrics, including frequency of question-and-answer visits and number of reminder alerts generated by the system, were recorded over the 6-week period and explored as surrogate indicators of self-management behavior but were not included in the primary adherence endpoint. Additional secondary outcomes were assessed at the 8-week endpoint: pain intensity during daily activities and squatting at 60° was measured using the Visual Analog Scale (VAS; 0-10);7 quadriceps muscle strength (concentric and eccentric peak torque) was evaluated using isokinetic dynamometry; knee function was assessed with the Kujala Patellofemoral Score (0-100); fatigue was measured using the Fatigue Severity Scale (FSS; 9 items, 7 points each). Additionally, a closed-ended adherence survey captured participant perceptions of factors influencing adherence

Inclusion criteria

• (1) Anterior knee pain or retro-patellar pain caused by at least two of the following activities: prolonged sitting with knee flexion, bilateral squatting, ascending and descending stairs, kneeling, running, and jumping;
• (2) presence of one of the following signs: patellar tenderness, friction pain, or twitching pain, positive single-leg squat test, or positive knee extension resistance test;
• (3) knee pain lasting more than 3 months;
• (4) knee pain score greater than 3 out of 10 on the VAS;
• (5) unilateral pain and symptoms.

Exclusion criteria

• (1) acute injury of the knee ligaments, joint capsule, bursa or meniscus;
• (2) knee extension or flexion contracture deformity, thus being unable to perform normal lower limb flexion and extension;
• (3) patellofemoral joint dislocation or subluxation;
• (4) any traumatic, inflammatory or infectious disease of the lower limbs;
• (5) a history of knee surgery;
• (6) a history of cardiovascular and cerebrovascular diseases, diabetes, tumors;
• (7) spinal cord or neurological injury.