Influence of flexing load position on the loading of cruciate ligaments at the knee—a graphics-based analysis

Abstract

Injuries of the cruciate ligaments of the knee, particularly the anterior cruciate ligament (ACL), is a common problem in young athletes. Therefore, identification of high-risk factors that lead to injury of the knee ligaments is required to avoid loading or protecting the ligaments from injury or during rehabilitation. In the present study, mechanics of the knee was analyzed for the influence of external flexing load positions on loading of the cruciate ligaments in the sagittal plane during 0° to 120° flexion. Experimental data was taken from literature. Mechanical equilibrium of the tibia was considered due to four types of forces, namely, a force in the patellar tendon, a ligament force, a tibio-femoral joint contact force, and an external flexing load applied distally on the tibia. The analysis suggests that during the muscle exercise at the knee, loading of the cruciate ligaments depends on flexion angle as well as on the position of external load on the tibia. Far distal placements of flexing loads on the tibia can stretch the ACL significantly at low flexion angles. The PCL is stretched during mid-to-high flexion range for all positions of the external flexing loads on the tibia. However, during the mid-flexion range, the effects of placement are modest. Therefore, rehabilitation exercises requiring protection of the ligaments need to pay attention to the position of external flexing load on the tibia as well as flexion angle at which the exercise is performed.