The anterior cruciate ligament in controlling axial rotation. An evaluation of its effect.

Changes in axial tibial rotation after anterior cruciate ligament sectioning were evaluated in 14 fresh human knee joints. Simulation of vertical stance in a quadriceps-stabilized knee was performed. Internal and external rotational torques were applied before and after anterior cruciate ligament sectioning. Pivot shift tests were done in the intact and anterior cruciate ligament sectioned knee. Results of pivot shift tests were all negative before sectioning and positive after isolated sectioning. No significant change in axial rotation occurred between the intact and sectioned knee for external rotation (P = 0.24) or internal rotation (P = 0.12). Presence of a load at the femoral housing in both the intact and ligament-sectioned knees caused a significant change in external rotation (P < 0.0001). No significant change was noted in internal rotation between loaded and unloaded states (P = 0.70). Total tibial rotation in the intact knee was noted to vary between 31 degrees at 0 degree of flexion and 42 degrees at 60 degrees of flexion. These results suggest that the anterior cruciate ligament does not play a significant role in limiting axial rotation and that rotational instability is not a major factor after isolated anterior cruciate ligament rupture.