The Human Posterior Cruciate Ligament Complex: An Interdisciplinary Study

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Abstract
To study the structural and functional properties of the human posterior cruciate ligament complex, we meas ured the cross-sectional shape and area of the anterior cruciate, posterior cruciate, and meniscofemoral liga ments in eight cadaveric knees. The posterior cruciate ligament increased in cross-sectional area from tibia to femur, and the anterior cruciate ligament area de creased from tibia to femur. The meniscofemoral liga ments did not change shape in their course from the lateral meniscus to their femoral insertions. The pos terior cruciate ligament cross-sectional area was ap proximately 50% and 20% greater than that of the an terior cruciate ligament at the femur and tibia, respectively. The meniscofemoral ligaments averaged approximately 22% of the entire cross-sectional area of the posterior cruciate ligament. The insertion sites of the anterior and posterior cruciate ligaments were evalu ated. The insertion sites of the anterior and posterior cruciate ligaments were 300% to 500% larger than the cross-section of their respective midsubstances. We determined, through transmission electron microscopy, fibril size within the anterior and posterior cruciate liga ment complex from the femur to the tibia. The posterior cruciate ligament becomes increasingly larger from the tibial to the femoral insertions, and the anterior cruciate ligament becomes smaller toward the femoral insertion. We evaluated the biomechanical properties of the femur-posterior cruciate ligament-tibia complex using 14 additional human cadaveric knees. The posterior cruciate ligament was divided into two functional com ponents : the anterolateral, which is taut in knee flexion, and the posteromedial, which is taut in knee extension. The anterolateral component had a significantly greater linear stiffness and ultimate load than both the postero medial component and meniscofemoral ligaments. The anterolateral component and the meniscofemoral liga ments displayed similar elastic moduli, which were both significantly greater than that of the posteromedial com ponent.