Simulation of Exoskeleton Alignment and its Effect on the Knee Extensor and Flexor Muscles

Area of Science:

• Biomechanics
• Musculoskeletal modeling
• Rehabilitation engineering

Background:

• Knee joint impairments affect muscle function, impacting mobility and recovery.
• Exoskeletons offer potential for powered assistance and alignment correction in rehabilitation.
• Understanding joint mechanics is crucial for effective exoskeleton design.

Purpose of the Study:

• To analyze the effects of knee joint impairments on knee extensor and flexor muscles.
• To investigate the correlation between joint parameters, movement, and forces for exoskeleton design.
• To simulate the impact of exoskeleton constraints on knee joint function.

Main Methods:

• Utilized OpenSIM 4.0 for musculoskeletal modeling and simulation.
• Introduced knee joint impairments in sagittal and transverse planes.
• Simulated an exoskeleton with a single hinge joint mimicking the knee.

Main Results:

• Alterations to the knee joint axis (±5.00 to -6.40 mm) caused meaningful but not significant changes in muscle stresses.
• Constraining knee motion to the sagittal plane increased vastus lateralis muscle force by up to 4.3%.

Conclusions:

• Knee joint axis deviations within the tested range have limited impact on muscle stress.
• Sagittal plane constraint by exoskeletons shows a modest increase in vastus lateralis force.
• These findings provide insights for designing effective knee joint exoskeletons.