A Systematic Review of in Vivo Anterior Cruciate Ligament Loading During Static, Slow-Speed and Athletic Tasks

Abstract

Purpose

An anterior cruciate ligament (ACL) injury is one of the most common severe knee injuries in sports. The purpose of this review was to summarize the studies that directly quantified in vivo ACL loading as a function of knee motion in healthy individuals during static, slow-speed and athletic tasks.

Methods

A systematic review of the literature in multiple databases was conducted using different combinations of the terms “anterior cruciate ligament” or “ACL” and “in vivo” combined with “tensile” “strain” “stress” “force” and “loading”.

Results

A total of 27 studies were identified. Eleven studies utilized strain sensors, while 16 studies applied imaging techniques. The numbers of studies for static or semi-static postures, slow-speed tasks, and athletic tasks were 12, 11 and 4, respectively.

Conclusion

There were strong and negative correlations between ACL elongation and knee flexion angles across different tasks. Peak ACL elongation mostly occurred when the knee flexion angle was minimal. Increased tibial anterior shear forces and patellar tendon forces would increase ACL loading when the knee is kept at a constantly small angle. In addition, a high patellar tendon force could be generated by preparatory quadriceps activation to load the ACL even when the lower extremity was not in contact with the ground during athletic tasks. Furthermore, while exercise modalities might affect peak ACL loading, the relationship between exercise intensities and ACL loading was complex and should not be assumed to be linear.

Funding

Foundation for the National Institutes of Health(P20GM103432); National Science Foundation(1933409); China Scholarship Council(China Scholarship Council)