Differences in transverse knee moment in healthy, ACL-deficient, and ACL-reconstructed patients during standing target matching

Lanier, Amelia
Journal Title
Journal ISSN
Volume Title
University of Delaware
Anterior cruciate ligament (ACL) injury is a common injury affecting nearly 250,000 Americans a year (Boden et al. 2000). Reconstructive surgery costs add up to approximately $1.5 billion annually not including initial evaluation or post-operative rehabilitation (Boden et al. 2000). The anterior cruciate ligament (ACL) limits anterior tibial translation and internal tibial rotation and so in the absence of the ACL rotational instability is common. Transverse knee moment, which has not been the focus of much research, can determine ACL-deficient (ACL-d) subjects’ ability or inability to compensate for this rotational instability. Target matching, both standing and seated, has provided insight for understanding neuromuscular control in both ACL deficient and reconstructed patients via EMG measurements (Williams et al. 2003; Macleod et al. 2011). We are now beginning to look at kinetic measures like transverse knee moment during this task in healthy, ACL-d and ACL reconstructed patients. Therefore the first aim of this work was to investigate transverse knee moment measured during a neuromuscular task in a healthy population. There is no difference in transverse knee moment between the right and left limbs of healthy subjects during standing target matching. Additionally, the shear forces generated by the mobilizing limb strongly correlate with the transverse knee moment of the stabilizing limb. These results indicate kinetic measures produced during standing target matching are dictated by target matching role not the limb itself. The second aim of this work was to evaluate transverse knee moment measured during a neuromuscular task in ACL-d patients. Our results show those with ACL injury have significantly higher internal rotation moments than healthy uninjured subjects. Increased rotational loads are present when subjects generate medial shear forces. This indicates an area of interest and the importance of joint stability in this medial direction. The third and final aim of this work was to evaluate changes in transverse knee moment during a neuromuscular task in ACL reconstructed patients. In particular we tested subjects within six months to one year post reconstruction when re-injury risk is highest (Salmon et al. 2005; Paterno et al. 2012). From this study we found those who undergo ACL reconstruction produce higher internal rotation moments when compared to uninjured subjects. We also see increased rotational loading at medial targets. In our group of subjects it appears that increased rotational loading occurs after injury and is not mitigated by reconstruction. The resulting increase in joint loading may have implications for high re-injury rates seen post reconstruction (Hewett et al. 2012) and high rotational loads have already correlated with increased cartilage loss (Henriksen et al. 2012). Producing force in a medial direction may be dangerous for those with ACL injury even after reconstruction and could be used to identify those at higher risk of re-injury. These results provide a basis to explore rotational loading corresponding to different graft types while exploring possible interventions to create joint stability in this medial direction.