Efficacy of a Squat Visual Biofeedback Program After ACL Reconstruction: Protocol for a Prospective, Parallel, Randomized Controlled Trial.

Background: Altered knee joint loading is pervasive and persistent after anterior cruciate ligament reconstruction (ACLR) and a significant driver for the development of knee osteoarthritis (OA). Purpose: To describe a prospective, parallel, randomized controlled trial aiming to evaluate the efficacy of an eight-week squat visual biofeedback program implemented early after ACLR. Study Design: Randomized controlled clinical trial. Methods: Thirty-four individuals (13-35 years of age) will be recruited for a prospective, parallel, randomized controlled trial. Embedded within progressive, criterion-based post-operative physical therapy, participants will be randomly allocated to an eight-week bodyweight squatting program either with or without visual biofeedback initiated when 50% weightbearing is allowed by the treating surgeon. Outcomes will be measured at pre- and post-intervention, six months post-ACLR, and nine months post-ACLR. The primary outcomes are 1) change in knee flexion moment impulse interlimb ratio during squatting at post-intervention, and 2) change in cartilage microstructure from pre-intervention to six months. Secondary outcomes include 1) knee flexion moment impulse interlimb ratio during squatting at six months post-ACLR, 2) peak knee flexion moment interlimb ratio during gait at post-intervention and six months post-ACLR, and 3) quadriceps strength at post-intervention and six months post-ACLR. Exploratory outcomes include knee range of motion and effusion, single-legged hop tests, daily physical activity, additional movement biomechanics, and patient-reported outcomes. Discussion: This study will assess the efficacy of an eight-week squat visual biofeedback program implemented early after ACLR. Findings will inform the future development and testing of comprehensive knee loading rehabilitation interventions that seek to optimize both the magnitude and frequency of knee joint loading to prevent early knee OA after ACL injuries. Level of Evidence: NA. Trial Registration: Clinicaltrials.gov reference: NCT05363683. Registered May 6, 2022.