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.