Abstract
A musculoskeletal model was developed to analyze the tensions of the knee joint ligaments during walking and to understand how they change with changes in the muscle forces. The model included the femur, tibia, patella and all components of cruciate and collateral ligaments, quadriceps, hamstrings and gastrocnemius muscles. Inputs to the model were the muscle forces, estimated by a static optimization approach, the external loads (ground reaction forces and moments) and the knee flexion/extension movement corresponding to natural walking. The remaining rotational and translational movements were obtained as a result of the dynamic equilibrium of forces. The validation of the model was done by comparing our results with literature data. Several simulations were carried out by sequentially removing the forces of the different muscle groups. Deactivation of the quadriceps produced a decrease of tension in the anterior cruciate ligament (ACL) and an increase in the posterior cruciate ligament (PCL). By removing the hamstrings, the tension of ACL increased at the late swing phase, while the PCL force dropped to zero. Specific effects were observed also at the medial and lateral collateral ligaments. The removal of gastrocnemius muscles produced an increase of tension only on PCL and lateral collateral ligaments. These results demonstrate how musculoskeletal models can contribute to knowledge about complex biomechanical systems as the knee joint.
Highlights
The knee joint is one of the most complex articulations in our body
The tibiofemoral contact force is in the order of 200–300% of body weight during walking where the muscle and ligament forces contribute to them for approximately 1/3 and 2/3, respectively
The comparison between our data and the reference data showed that our tibiofemoral contact force in the “All muscles” condition was larger than the reference one
Summary
The relative displacements of distal femur and proximal tibia are determined by the shape of bone surfaces and by ligaments and muscle forces. The femoral condyles and the tibial plateau are not at all congruent and allow the proximal tibia to slide forward and backwards and rotate around its longitudinal axis (internal/external rotation). That means that the ligaments must be stiff enough to prevent joint dislocation under load, but they are positioned in such a way that the main flexion-extension movement is not restricted
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