The anterior cruciate ligament does play a role in controlling axial rotation in the knee

This study deals with the influence of peroperative ligament tension on total tibial rotation at different knee flexion angles. Fourteen human cadaver knees with a mean age of 56 years (range 42-84 years) were examined. The cadaver knees were subjected to internal/external (i/e) rotational torque of 6 Nm, at 10, 30, 50, 70 and 90 deg of knee flexion. The mean total i/e rotation with the anterior cruciate ligament (ACL) intact at 10 deg of knee flexion was 30.4 deg and after removing the ACL, 33.1 deg. At 10 and 30 deg of knee flexion, the increase in i/e rotation was significant, while there was no significant difference in mean values at greater knee flexion. Ligament reconstruction with a tension of 5 N at 30 deg of knee flexion using either the over the top or through the femoral condyle reconstructive procedure restored normal tibial rotation. With increased graft tension the knee motion was increasingly restricted at low angles of knee flexion. Our results indicate that the ACL does play a role in limiting axial rotation, and even minor tensioning forces introduced in any of the two ACL reconstructions used produced restricted knee motion.