The purpose of this study is to determine the effect of modifiable risk factors on knee function, osteoarthritis, and re-rupture of the anterior cruciate ligament (ACL) following ACL reconstruction.

Disruption of the anterior cruciate ligament (ACL) is among the most frequent musculoskeletal injuries affecting physically active men and women. An estimated 200,000 ACL reconstructions (ACLR) are performed annually, and the incidence of this injury is roughly 1 in 3000 per year. ACL injury has both immediate and long-term implications for an injured person's quality of life, their risk for osteoarthritis (OA), and long-term disability. Currently, ACLR is recommended as the standard of care following an ACL tear based on evidence for improved instrumented laxity, the desire to return to sports play, and evidence for a reduction in future knee injuries.

In this research we propose to identify risk factors measurable at the time of injury/surgery in order to estimate the magnitude of the effect of these factors on important quality of life and clinical outcomes (e.g.,OA and incidence of additional surgery) 2 to 10 years after a patient's ACL reconstruction.

AIM 1. To identify risk factors for reduced quality of life 2-20 yrs post-ACLR, from information available at the time of surgery; including the characteristics of the patients (age, gender, body mass index, activity level, clinical knee alignment) and their injuries (concurrent meniscus, articular cartilage, and collateral ligament injuries), and treatment decisions made during the initial surgery (e.g., graft choice, meniscus and articular cartilage treatments).

AIM 2. To identify risk factors for symptoms and signs of osteoarthritis 2-20 years post-ACLR, from information available at the time of surgery; including the characteristics of the patients (as above) and their injuries (as above), and treatment decisions made during ACLR (as above).

AIM 3. To identify risk factors for recurrent ligament disruption and additional arthroscopic knee surgeries of the ACLR knee, from among the characteristics of the patients (as above), their initial injuries (as above), and treatment decisions made during ACLR (as above).

The overarching goal of this study is to establish evidence-based medicine practices of counseling patients on prognosis, guiding surgeons on treatment of meniscus and articular cartilage injuries, and post-surgical care, as well as the appropriate evidence for future interventional trials in the targeted subset of ACLRs with poorer outcomes.

Inclusion Criteria:

- All ACL-deficient candidates scheduled for a unilateral ACL reconstruction at one of the participating MOON sites.

Exclusion Criteria:

• Persons undergoing a simultaneous bilateral ACL reconstruction
• Patients less than 10 years old and older than 80 years old
• Patients unwilling or unable to complete their follow-up questionnaire

All eligible ACL-deficient candidates scheduled for a unilateral ACL reconstruction at one of the participating MOON sites.