ROLE OF THE MEDIAL STRUCTURES IN THE INTACT AND ANTERIOR CRUCIATE LIGAMENT-DEFICIENT KNEE - LIMITS OF MOTION IN THE HUMAN KNEE

We measured motion limits in human cadaveric knees before and after se ctioning the anterior cruciate ligament and the medial structures. Sec tioning the medial collateral ligament in an anterior cruciate ligamen t-deficient knee increased the anterior translation limit at 900 of fl exion but not at 30-degrees of flexion. The tibia displaced straight a nteriorly without exhibiting the coupled internal rotation that occurr ed in intact and anterior cruciate ligament-deficient knees. A lateral 15 N-m abduction moment produced a coupled external rotation in the m edial collateral ligament-deficient knee. This was in marked contrast to intact, anterior cruciate ligament-deficient, or combined medial co llateral ligament and anterior cruciate ligament-deficient knees, in w hich an abduction moment produced a coupled internal rotation. Section ing only the medial collateral ligament caused a small but significant increase in the abduction rotation limit, whereas larger increases in the abduction rotation limit occurred when the posterior oblique liga ment and posterior medial capsule were cut in addition to the medial c ollateral ligament. Cutting the medial collateral ligament increased t he external rotation limit. The increase was independent of whether th e anterior cruciate ligament was intact or sectioned. Subsequent cutti ng of the posterior oblique ligament and posterior medial capsule furt her increased the external rotation limit.