摘要： Over the past 3 decades, our ability to noninvasively image structures of the musculoskeletal system has facilitated clinical diagnoses and provided insight into the success of various therapeutic interventions. As imaging modalities are refined and novel approaches are introduced, imaging technologies can provide objective measures to better understand the natural history and mechanisms of diseases and optimize and evaluate their treatment. While traditional radiography and computed tomography are commonly used to evaluate the integrity of bony structures, recent advances include biplanar videoradiography, which can now be used to directly track 3-dimensional joint motion in vivo with a high degree of accuracy.11 As such, biplanar videoradiography has been applied to study the progression of arthrosis after anterior cruciate ligament (ACL) injury.4 Based on recent technological advances, ultrasound is now being used to measure cartilage thickness to study the progression of arthrosis in vivo after ACL injury.8 Likewise, there has been a real boon in the use of magnetic resonance imaging (MRI) to evaluate anatomic, biomechanical, and compositional interactions among the structures of an injured joint. For example, MRI has been used to evaluate compositional changes of the articular cartilage in the injured joint in relation to changes in loading during gait.13 These kinds of studies provide opportunities to better understand mechanisms of posttraumatic osteoarthritis following joint injury. Furthermore, MRI has been recently applied to gain insight into the mechanisms of ACL injury.9 By using the projections of the bone bruises that occurred during ligament rupture onto the articular surfaces within the 2 compartments of the knee via models derived from 3-dimensional MRI scans, the position of the tibia relative to the femur at the time of injury can be determined.9 MRI has also been used to evaluate the structural and mechanical integrity of the menisci3 and ACL grafts after surgery.1