Abnormal Rotational Knee Motion during Running after Anterior Cruciate Ligament Reconstruction

BACKGROUND: The effectiveness of anterior cruciate ligament reconstruction for restoring normal knee kinematics is largely unknown, particularly during sports movements generating large, rapidly applied forces. HYPOTHESIS: Under dynamic in vivo loading, significant differences in 3-dimensional kinematics exist between anterior cruciate ligament-reconstructed knees and the contralateral, uninjured knees. STUDY DESIGN: Prospective, in vivo laboratory study. METHODS: Kinematics of anterior cruciate ligament-reconstructed and contralateral (uninjured) knees were evaluated for 6 subjects during downhill running 4 to 12 months after anterior cruciate ligament reconstruction, using a 250 frame/s stereoradiographic system. Anatomical reference axes were determined from computed tomography scans. Kinematic differences between the uninjured and reconstructed limbs were evaluated with a repeated-measures analysis of variance. RESULTS: Anterior tibial translation was similar for the reconstructed and uninjured limbs. However, reconstructed knees were more externally rotated on average by 3.8 +/- 2.3 degrees across all subjects and time points (P =.0011). Reconstructed knees were also more adducted, by an average of 2.8 +/- 1.6 degrees (P =.0091). Although differences were small, they were consistent in all subjects. CONCLUSIONS: Anterior cruciate ligament reconstruction failed to restore normal rotational knee kinematics during dynamic loading. CLINICAL RELEVANCE: Although further study is required, these abnormal motions may contribute to long-term joint degeneration associated with anterior cruciate ligament injury/reconstruction.