Posterior Horn Meniscus Centroid Position Is Altered Soon After Noncontact ACL Injury in Males and Females

Anterior cruciate ligament (ACL) injury and subsequent changes in the magnitude and distribution of contact stress about the articular surfaces of the knee are associated with post-traumatic osteoarthritis. Soon after ACL injury, changes in tibial articular cartilage thickness occur that can be explained, in part, by abnormal positioning of the tibia relative to the femur. However, little is known about the effects of ACL injury on the positions of the menisci. The purpose of this case-control study was to determine the effect of ACL injury on posterior horn meniscus centroid (PHMC) position relative to the tibia in males and females. ACL-injured and matched control subjects with normal knees underwent bilateral magnetic resonance imaging soon after the index injury and prior to ACL reconstruction. The PHMC position was defined in three dimensions at the point of maximal tibial articular cartilage concavity in the lateral and medial compartments of the knee. In control subjects, there were no significant differences in PHMC position between knees in the lateral and medial compartments. In ACL-injured knees, there were significant posterior-directed changes in PHMC position in both compartments for males and females when compared to their contralateral normal knees. These changes in PHMC position may alter the distribution of articular cartilage contact stress and explain a portion of the changes in knee biomechanics and cartilage thickness that occur following ACL injury. In addition, these findings suggest that the menisci should not be used as landmarks to establish regions of interest when measuring cartilage thickness and matrix components.