In-situ Forces in Human Knee Ligaments During an Instability Test. Measurement using Robotics.

In-situ forces in knee ligaments during anterior and posterior drawer tests were determined under the priciple of superposition. Sequential section of ligaments of two amputated knees was performed, while the three-dimensional path of intact knee motion was reproduced using a robotic system. Under 100N of anterior force, the in-situ force in the anterior cruciate ligament (ACL) was 88N at 0° of flexion and decreased to 54N at 90° of flexion ; however the in-situ force in the medial collateral ligament increased with increasing flexion angle. The posterior quarter of the anteromedial portion of the ACL and posterolateral portion of the ACL were loaded under unterior force. Under 100N of posterior force, the in-situ force in the posterior cruciate ligament (PCL) was 30N at 0° of flexion, and increased to 105N at 90° of flexion. The anterolateral portion of the PCL was loaded under posterior force. All data were important for a better understanding of the mechanism of the knee instability test and for improvement of the diagnosis of the ligament injury.