Anterior cruciate ligament response due to forces resulting from quadriceps muscle and ground reaction

Instrumented cadaveric knees were used to quantify the association between quadriceps muscle force, ground reaction force, and strain in anterior cruciate ligament (ACL) through in vitro simulation of a vertical jump-landing process in a dynamic loading simulator. The research question for this project was set: “Can the ACL strain be influenced by the unopposed quadriceps force (QMF), low knee flexion angle, and constant ground reaction force (GRF)?” Fourteen cadaveric knees were mounted in the custom made dynamic loading simulator to measure strain on the anteromedial bundle of the ACL using a differential variable reluctance transducer (DVRT). An I-Scan pressure transducer (Model 4000) was used to measure contact pressure and area in the tibiofemoral joint. A 3D nonlinear dynamic finite element knee model was developed, and the results from this model were validated with the experimental results. The influence of the intrinsic risk factors, like the lateral tibial slope, medial tibial slop, and the curvature of the medial compartment do exist on the loading in ACL at the time of applying quadriceps muscle force. It was also observed that the tibia rotates internally prior to landing and during landing. During the landing phase, the peak pressure on the lateral compartment is very high, compared with the medial compartment. During the landing phase, both the contact area and pressure increases in the tibiofemoral joint. The influence of pressure induced joint conformity is also justified. It can be concluded from the obtained results from the experimental and numerical works that the unopposed quadriceps muscle forces coupled with ground reaction force at low knee flexion angle cannot cause ACL injury. Joint compressive loads induced by large muscle forces and GRF introduces the joint conformity, and this joint conformity produces the primary restraint against anterior tibial translation at low flexion angles along with menisci.