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The Effect of Anterior Cruciate Ligament Deficiency on the in Vivo Elongation of the Medial and Lateral Collateral Ligaments

Background Although anterior cruciate ligament deficiency has been shown to lead to joint degeneration, few quantitative data have been reported on its effect on soft tissue structures surrounding the knee joint. Hypothesis Anterior cruciate ligament deficiency will alter the deformation of both collateral ligaments during in vivo weight-bearing knee function from 0° to 90°. Study Design Controlled laboratory study. Methods Six patients who had acute anterior cruciate ligament injury in 1 knee with the contralateral side intact participated in this study. Using magnetic resonance and dual orthogonal fluoroscopic imaging techniques, we measured the length of the fiber bundles of the superficial medial collateral ligament, deep medial collateral ligament, and lateral collateral ligament of the 6 patients; the healthy contralateral knee of each patient served as a control. Results Anterior cruciate ligament injury caused a significant elongation of the fiber bundles of the superficial and deep medial collateral ligament at every flexion angle. In contrast, the lateral collateral ligament fiber bundles shortened after anterior cruciate ligament injury. Conclusion The altered deformations of the collateral ligaments associated with the changes in tibiofemoral joint kinematics after anterior cruciate ligament injury demonstrate that deficiency of 1 of the knee joint structures upsets the in vivo knee homeostasis. Clinical Relevance Restoring normal knee kinematics after anterior cruciate ligament reconstruction is critical to restore the normal function of the collateral ligaments.