Development of an open-source cosimulation method of the knee

Area of Science:

• Biomechanics
• Musculoskeletal modeling
• Computational mechanics

Background:

• Accurate estimation of soft tissue loads in the knee is essential for understanding joint mechanics.
• Existing models often treat musculoskeletal dynamics and tissue mechanics separately, potentially limiting accuracy.

Purpose of the Study:

• To implement and validate an open-source cosimulation framework for the knee.
• To investigate the impact of coupled musculoskeletal and tissue mechanics on computed cartilage loads.

Main Methods:

• Replaced OpenSim's generic knee model with a discrete element knee model (6-DOF tibiofemoral, 1-DOF patellofemoral).
• Employed a cosimulation approach, simultaneously solving neuromusculoskeletal dynamics and knee mechanics using a computed muscle control (CMC) algorithm.
• Compared serial and cosimulation approaches for a simple knee flexion movement.

Main Results:

• The cosimulation framework successfully coupled rigid body dynamics and soft tissue loads.
• Significant differences in computed cartilage loads were observed compared to serial approaches.
• Demonstrated the influence of computational methods and accurate degree-of-freedom acquisition on soft tissue load estimation.

Conclusions:

• Coupling musculoskeletal and tissue mechanics is critical for accurate knee cartilage load prediction.
• The choice of computational method and the fidelity of knee joint data significantly impact soft tissue load estimations.
• This validated cosimulation framework provides a robust tool for future knee biomechanics research.