Knee joint is the most common site of injury in children and adolescents and accounts for up to 60% of all sports-related injuries in this population. Ruptures of the anterior cruciate ligament (ACL) are among the most frequent knee injuries in pediatric population with up to 10 times greater prevalence in females than males. These injuries are often immediately disabling and are associated with significant short- and long-term clinical compilations such as increased risk of posttraumatic osteoarthritis (OA), despite our best current treatment methods. Several unique anatomical features of the knee joint, including tibial slope and femoral notch size, have shown to affect joint and ACL loading and risk of injury. Despite the well-established role of these anatomical features on ACL injury risk, it remains unclear how these anatomical features change during skeletal growth and maturation. We are proposing to systematically investigate how age and sex affect multiple prominent anatomical features of the knee joint in children and adolescents. This will be done retrospectively by analyzing the Magnetic Resonance (MR) images of the knees of patients who underwent a knee MRI at Boston Children’s Hospital. The 3D MR image stacks will be used to measure a comprehensive set of anatomical indices of the knee joint based on previously established techniques. The associations between age and each of the quantified anatomical indices will be assessed. The age-dependent changes in knee anatomy will be compared between boys and girls as well as between those who had an ACL injury and those with healthy uninjured knees. Findings will help to better understand how prominent anatomical features of the knee joint, in particular those identified as risk factors for ACL injury, are being developed and/or changed during skeletal growth and maturation. Findings will also improve our knowledge of how sex may affect the age dependent changes in knee anatomy. The outcomes of this work will improve our knowledge on how and when anatomy becomes different between subjects at low risk of ACL injury and “at risk” population. Such improved knowledge can be used to develop novel risk screening models to more effectively identify children at high risk of ACL injury based on their anatomical profile. Individuals with high-risk bony anatomy can be subjected to neuromuscular and biomechanical interventions early on to minimize their risk of sustaining and ACL tear.