Prediction of Knee Kinematics at the Time of Noncontact Anterior Cruciate Ligament Injuries Based on the Bone Bruises

Biomechanical risk factors associated with the alignment and position of the knee for anterior cruciate ligament (ACL) injury are still not conclusive. As bone bruises identified on magnetic resonance imaging (MRI) following acute ACL injury could represent the impact footprint at the time of injury. To improve understanding of the ACL injury mechanism, we aimed to determine the knee kinematics during ACL injury based on the bone bruises. Knee MRI scans of patients who underwent acute noncontact ACL injuries were acquired. Numerical optimization was used to match the bone bruises of the femur and tibia and predict the knee positions during injury. Knee angles were compared between MRI measured position and predicted position. The knee flexion, abduction, and external tibial rotation angles were significantly greater in the predicted position than that in MRI measured position. Relative to MRI measured position, patients had a mean of 34.3 mm of anterior tibial translation, 4.0 mm of lateral tibial translation, and 16.0 mm superior tibial translation in the predicted position. The results suggest that knee valgus and external tibial rotation accompanied by knee flexion are high-risk movement pattern for ACL injury in patients with lateral compartment bone bruising in conjunction with ACL injury.