High Axial Loads while Walking Increase Anterior Tibial Translation in Intact and Anterior Cruciate Ligament-Deficient Knees

Purpose To evaluate the effect of high axial loading (AL) on anterior tibial translation (ATT) according to the increase in knee flexion and the effect of valgus stress (VS) and internal rotation (IR) combined with high AL in intact and anterior cruciate ligament (ACL)-deficient knees according to the increase in knee flexion. Methods We used 10 fresh-frozen, human cadaveric knees. Different loading conditions (134-N anterior drawer, 1,000-N AL, 10-Nm VS, and 5-Nm IR) were sequentially combined, and ATT was measured at 0°, 15°, 30°, 45°, and 60° of flexion in the intact and ACL-deficient knees. Results ATT increased significantly by adding high AL in intact knees (P =.001) and ACL-deficient knees (P <.0001) according to the change in flexion angle (P <.0001). Under high AL, ATT in the ACL-deficient knees was significantly larger than that in the intact knees for all loading conditions, and it also increased gradually according to the increase in knee flexion (P =.0001). ATT increased significantly after adding IR or VS with high AL in intact knees (VS, P =.002; VS/IR, P =.03) and ACL-deficient knees (VS, P =.0004) at some of the flexion angles. Conclusions The added high AL increased ATT in intact and ACL-deficient knees from 0° to 60° of flexion. The effect of high AL on ATT became greater in ACL-deficient knees than in intact knees, and ATT also gradually increased according to the increase in knee flexion from 0° to 60°. In both the intact and ACL-deficient knees, ATT increased significantly after valgus stress or IR from 0° to 60°. Clinical Relevance ATT during weight bearing increases stress to the ACL, which worsens with valgus stress and/or IR forces. This finding should be considered when one is studying ACL injury mechanisms, as well as prescribing rehabilitation after ACL surgery.