Strain distributions in the anterolateral soft tissue structures of the knee are dependent on knee flexion angle and loading pattern

Purpose Quantify the regional strains of the anterolateral structures in response to clinically relevant kinematic testing of cadaveric knees. Method Zirconium dioxide beads were implanted into the following tissues of six, ACL intact, specimens: (1) ALL; (2) Capsulosseous IT Band; (3) Kaplan fibres and (4) lateral meniscus. The specimens were then secured within a CT‐compatible knee joint motion simulator, and a baseline image of the joint was acquired. The following series of loading conditions were applied: (1) 5 Nm internal rotation; (2) 100 N anterior translation and (3) a simulated pivot shift consisting of 100 N compression, 5 Nm internal rotation, 10 Nm valgus rotation and 100 N anterior translation. Each condition was tested at 0°, 15° and 30° of knee flexion with an image acquired at each of the load targets. The centroid of each of the beads and the change in length between adjacent beads before and after an applied load was quantified and represents the tissue strain. Friedman's ranked analysis of variance was performed to determine if statistical differences in strain occurred between the different knee flexion angles in each of the tissues. Results Internal rotation did not significantly affect the strain in any of the tissues across any of knee flexion angle. There was a statistically significant difference in the mean strains within the mid‐body of the lateral meniscus, during the application of anterior translation, between 0° and 30° of knee flexion. Finally, the pivot shift generated a significant main effect of knee flexion angle within the Kaplan fibres, although the post hoc tests could not identify where the differences occurred. Conclusions The lateral meniscus and the Kaplan fibres displayed regional differences in the strain that were dependent on both the knee flexion angle and the loading condition, suggesting that the combined stabilising response of these tissues is synergistic, secondary to the ACL. Level of Evidence N/A.