The Role of the Medial Meniscus in Anterior Knee Stability

Abstract

Background: Few studies have compared the force distribution between the anterolateral, posterolateral, and medial structures of the knee.

Purpose: To investigate the important structures in an intact knee contributing to force distribution in response to anterior tibial load.

Study design: Controlled laboratory study.

Methods: Nine fresh-frozen cadaveric knee specimens underwent robotic testing. First, 100 N of anterior tibial load was applied to the intact knee at 0°, 15°, 30°, 60°, and 90° of knee flexion. The anterior cruciate ligament (ACL), anterolateral capsule, lateral collateral ligament, popliteal tendon, posterior root of the lateral meniscus, superficial medial collateral ligament, posterior root of the medial meniscus (MM), and posterior cruciate ligament were then completely transected in sequential order. After each transection, the authors reproduced the intact knee motion when a 100-N anterior tibial load was applied. By applying the principle of superposition, the resultant force of each structure was determined based on the 6 degrees of freedom force/torque data of each state.

Results: At every measured knee flexion angle, the resultant force of the ACL was the largest of the tested structures. At knee flexion angles of 60° and 90°, the resultant force of the MM was larger than that of all other structures with the exception of the ACL.

Conclusion: The MM was identified as playing an important role in response to anterior tibial load at 60° and 90° of flexion.

Clinical relevance: In clinical settings, the ACL of patients with a poorly functioning MM, such as tear of the MM posterior root, should be monitored considering the large resultant force in response to an anterior tibial load.

Keywords: anterior cruciate ligament; anterior tibial load; biomechanics; fresh-frozen cadaver; lateral meniscus; medial collateral ligament; medial meniscus; robotic system.

Figure 1.

Robotic testing system with a right knee specimen. The manipulator, which works with a universal force-torque sensor, was placed on the end-effector. The tibia was fixed to the end-effector, and the femur was fixed to the lower part of the device using metal clamps.

Figure 2.

Resultant forces of knee structures in response to anterior tibial loading. Error bars indicate SDs. Brackets indicate significant differences within each knee flexion angle. *Significantly greater than all other structures at each knee flexion angle (excluding other * structures). ACL, anterior cruciate ligament; ALC, anterolateral capsule; LCL, lateral collateral ligament; LMPR, posterior root of the lateral meniscus; MCL, medial collateral ligament; MMPR, posterior root of the medial meniscus; PCL, posterior cruciate ligament.