In this study we will examine patients who have undergone unilateral ACL reconstruction surgery to determine which structural and functional characteristics of the knee two and ten years post reconstruction surgery, aspects of the original injury and repair, and patient characteristics are risk factors for osteoarthritis after ACL reconstruction surgery.

The purpose of this study is identify risk factors for signs and symptoms of osteoarthritis two and ten year post ACL reconstruction from information available at the time of surgery; including patient characteristics (age, gender, body mass index (BMI), activity level, clinical knee alignment), their injuries ("pop" heard at the time of injury, concurrent meniscus, articular cartilage, and collateral ligament injuries), and treatment decisions made during the initial surgery (e.g. meniscus and articular cartilage treatments.)

Primary outcome measures will be the Western Ontario and McMaster Universities Arthritis Index (WOMAC) pain and stiffness subscales and joint space width measured on weight-bearing radiographs.

Secondary outcome measures will include the knee related quality of life subscale of the Knee Injury and Osteoarthritis Score (KOOS) and Kellgren-Lawrence grading from weight-bearing radiographs.

Inclusion Criteria:

• Had primary unilateral ACL reconstruction performed by Dr. Kurt Spindler (Vanderbilt University), Dr. Christopher Kaeding (The Ohio State University), Dr. Rick Parker (Cleveland Clinic), Dr. Jack Andrish (Cleveland Clinic), Dr. Rick Wright (Washington University in St. Louis), or Dr. Matthew Matava (Washington University in St. Louis)
• 14-55 years of age at the time of follow-up

Exclusion Criteria:

• less than 14 years or greater than 55 years
• non-active or unable to participate for health reasons

Participants enrolled in the Multicenter Orthopaedic Outcomes Network cohort by one of three surgeons and meeting eligibility criteria