PROJECT SUMMARY Anterior cruciate ligament (ACL) rupture is a common knee injury in sports that is usually surgically treated with ACL reconstruction. Most patients expect to resume pre-injury sport participation after ACL reconstruction, yet only 65% do, and up to 20% of those sustain another ACL injury. Fear of re-injury contributes to the sub- optimal return-to-sport outcomes, giving it clinical importance and raising awareness of it. Yet a range of negative (e.g., anger, fear/kinesiophobia) and positive (e.g., motivation, self-efficacy/confidence) psychological responses are typical after ACL reconstruction. It is important to effectively manage psychological responses because they impact behaviors, and in turn, outcomes. Standard ACL reconstruction rehabilitation strictly focuses on exercise for knee impairments, and clinicians do not feel prepared to help patients manage their psychological responses. Also, patients lack an understanding of psychological responses and helpful mental skills. Clinicians and patients both require training to address the unmet need for psychological support in ACL reconstruction rehabilitation. The objective of this study is to examine the efficacy of Rehabilitation with Exercise and Psychological Support (REPS), a rehabilitation approach that integrates exercise with psychological support provided by a clinician and patient training videos. The central hypothesis is that REPS will facilitate better psychological response (Specific Aim 1) and knee function (Specific Aim 2) than Standard Rehabilitation after ACL reconstruction. The feasibility, acceptability, and fidelity of implementing REPS will be explored. This is a pilot randomized controlled trial of 60 patients with ACL reconstruction who receive REPS or Standard Rehabilitation. Both groups will perform exercise per a standard rehabilitation protocol. REPS clinicians (n=4) will receive didactic training and mentorship from the study team on a psychologically informed practice approach for assessment and treatment, including patient-centered communication and cognitive- behavioral techniques. Patients in REPS will receive training on mental skills to improve the psychological response in videos created by the study team. Baseline testing will be immediately before the first rehabilitation visit, and primary follow-up testing will be 6 months post-surgery, when rehabilitation typically completes. This study will generate knowledge about a rehabilitation approach intended to provide psychological support to patients during ACL reconstruction rehabilitation. The study has good potential to be impactful because it targets an unmet need in ACL reconstruction rehabilitation that contributes to clinical outcomes. The REPS intervention is innovative because it is administered within a clinical setting, engages both patients and clinicians with pragmatic training methods, and could enhance patient-clinician communication to strengthen therapeutic alliance for bette...