UCSF

Purpose

To investigate the longitudinal changes in landing mechanics and knee kinematics for patients both before and 3 years after anterior cruciate ligament reconstruction (ACLR) and to investigate the association between changes in landing mechanics and magnetic resonance knee kinematics.

Methods

Thirty-one ACLR patients were included in the study. All patients underwent magnetic resonance imaging and biomechanical analysis of a drop-landing task using the injured knee and contralateral knee preoperatively and at 6 months and 3 years after ACLR. For evaluations of knee joint anteroposterior laxity, tibial position was calculated using quantitative loaded magnetic resonance methods.

Results

The ACLR knee exhibited a significantly lower peak vertical ground reaction force and peak external knee flexion moment and angle at 6 months compared with the contralateral knee; however, the differences were resolved at 3 years. Tibial position was significantly more anterior on the injured side, and the side-to-side difference (SSD) in tibial position exhibited a significant increase from 6 months to 3 years. Among ACLR knees, a greater SSD in peak knee flexion moment at 6 months was associated with an increase in the SSD in anterior tibial translation from 6 months to 3 years.

Conclusions

Although landing mechanics and clinical outcomes recovered in patients with ACLR in this study, anteroposterior translation failed to be restored at 3 years after surgery. In addition, patients who have low knee flexion moments in early stages could have greater anteroposterior laxity.

Clinical relevance

Because of the adverse consequences of abnormal knee kinetics on anterior laxity after ACLR, efforts to improve knee movement patterns should be initiated.