Skeletally immature athletes do get major knee injuries. Hemarthrosis is associated with peripheral meniscal tears, anterior cruciate ligament ruptures, tibial tubercle avulsion injuries, and patellar/femoral osteochondral fractures and cannot be ignored. The primary diagnostic tool for patients with a knee injury is a clinical examination by a physician well trained in knee evaluation. MR imaging has significant limitations in this age group. The algorithm for anterior cruciate ligament injury treatment must take into account the patient's physiologic maturity, not chronological age.