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Development of an Open-Source, Discrete Element Knee Model

Objective: Biomechanical modeling is an important tool in that it can provide estimates of forces that cannot easily be measured (e.g., soft tissue loads). The goal of this study was to develop a discrete element model of the knee that is open source to allow for utilization of modeling by a wider audience of researchers. Methods: A six degree-of-freedom tibiofemoral and one degree-of-freedom patellofemoral joint were created in OpenSim. Eighteen ligament bundles and tibiofemoral contact were included in the model. Results: During a passive flexion movement, maximum deviation of the model from the literature occurred at the most flexed angle with deviations of 2° adduction, 7° internal rotation, 1-mm posterior translation, 12-mm inferior translation, and 4-mm lateral translation. Similarly, the overall elongation of the ligaments agreed with literature values with strains of less than 13%. Conclusion: These results provide validation of the physiological relevance of the model. Significance: This model is one of the few open source, discrete element knee models to date, and has many potential applications, one being for use in an open-source cosimulation framework.