Journal of Orthopaedic Science

Akihiro Kanamori, Masataka Sakane, Jennifer Zeminski, Theodore W. Rudy, and Savio L-Y. Woo


The anterior cruciate ligament (ACL) is the major contributor to limit excessive tibial translation (ATT) when the knee is subjected to an anterior tibial load. However, the importance of the medial and lateral structures of the knee can also play a significant role in resisting anterior tibial loads, especially in the event of an ACL injury. Therefore, the objective of this study was to determine quantitatively the increase in the in-situ forces in the medial collateral ligament (MCL) and posterolateral structures (PLS) of the knee associated with ACL deficiency. Eight fresh-frozen cadaveric human knees were subject to a 134-N anterior tibial load at full extension and at 15ƒ, 30ƒ, and 90ƒ of knee flexion. The resulting 5 degrees of freedom kinematics were measured for the intact and the ACL-deficient knees. A robotic/universal force-moment sensor testing system was used for this purpose, as well as to determine the in-situ force in the MCL and PLS in the intact and ACL-deficient knees. For the intact knee, the in-situ forces in both the MCL and PLS were less than 20 N for all five flexion angles tested. But in the ACL-deficient knee, the in-situ forces in the MCL and PLS, respectively, were approximately two and five times as large as those in the intact knee (P< 0.05). The results of this study demonstrate that, although both the MCL and PLS play only a minor role in resisting anterior tibial loads in the intact knee, they become significant after ACL injury.