Anterior-posterior stiffness and laxity of the knee after major ligament reconstruction.

We recorded anterior-posterior force-versus-displacement curves at 20 and 90 degrees of flexion preoperatively and three years after major ligament reconstruction in patients with documented absence of the anterior cruciate ligament. Patients who had an extracapsular stabilization procedure alone showed no significant changes in laxity or stiffness of the injured knee in either position of flexion. Those who underwent reconstruction of the absent anterior cruciate ligament utilizing the middle or medial one-third of the patellar ligament in addition to the extracapsular procedure showed a significant decrease in anterior laxity and increase in anterior stiffness of the injured knee at 20 degrees of flexion. These changes in stability were not observed at 90 degrees of flexion. Six patients with a cruciate substitution had improved laxity and stiffness values at one year postoperatively which were unchanged at three years. At three-year follow-up the increases in activity scores, decreased feelings of giving-way and pain, and elimination of the pivot shift were comparable in both groups of patients.