Lachman´s ACL test: A multibody simulation

Diagnosing a torn Anterior Cruciate Ligament (ACL) of the knee is a difficult task which is usually performed by physical therapist using physical manipulation of the knee. To help training physical therapy students recognizing the difference between an intact and torn ACL this work proposes a simplified physical model to be fabricated. The model is proposed to replicate the Lachman´s test which measures the anteroposterior displacement between the femur and the tibia in a specific knee configuration. In preparation for fabrication a set of in-silico experiments were performed using SimWise software. Including the ACL constraint in the simulation provided a forward displacement of 7.29mm between femur and tibia. Simulations without the ACL produced a displacement of 12.65mm. These results are in agreement with the literature and provide a solid theoretical basis for the fabrication of the physical prototype.