Three-spring flexion-resistance module for knee orthoses design and evaluation

Area of Science:

• Biomedical Engineering
• Orthotics and Prosthetics
• Mechanical Design

Background:

• Existing passive knee orthoses offer limited energy dissipation and load regulation for high-demand activities.
• Joint instability necessitates assistive devices that can manage flexion loads effectively.

Purpose of the Study:

• To design and validate a compact, three-spring mechanism for knee orthoses.
• To enhance energy absorption, provide quasi-passive flexion resistance, and redistribute loads.

Main Methods:

• Combined analytical modeling, finite-element simulations (ANSYS Explicit Dynamics®), and experimental testing.
• Developed a mechanism with two compression and one tension spring in an aluminum frame.
• Validated through pilot functional testing with adult volunteers performing one-leg rise and deep-squat tasks.

Main Results:

• Simulations and experiments showed close agreement (<3% deviation) in force and deformation.
• The mechanism provided an estimated 70.54 Nm passive flexion resistance, reducing required torque by 48.22% compared to post-ACLR data.
• Peak stresses were below aluminum yield strength; functional tests indicated moderate perceived assistance (VAS scores ~37-42).

Conclusions:

• The proposed multi-spring mechanism demonstrates feasibility as a compact, assistive knee orthosis concept.
• The design offers measurable quasi-passive resistance and withstands high-flexion loading.
• Further research is warranted for fatigue assessment, optimization, and clinical validation with objective outcomes.