Development of four-bar polycentric knee joint with stance-phase knee flexion

Area of Science:

• Biomedical Engineering
• Prosthetics and Orthotics
• Biomechanics

Background:

• Conventional 4-bar polycentric knees with SACH feet lack stance-phase knee flexion.
• This limitation results in unnatural gait and reduced stability for individuals with amputations.

Purpose of the Study:

• To propose and validate a novel 4-bar polycentric knee with stance-phase flexion (4BSF).
• To enable a gait pattern closer to able-bodied individuals, incorporating both stance and swing-phase knee flexion.

Main Methods:

• Conceptual design of the 4BSF, repositioning the instantaneous center of rotation (ICR) during the stance phase.
• Positioning the ICR in front of the ground reaction force (GRF) to initiate loading response knee flexion.
• Validation through a single-subject pilot study in a gait analysis laboratory.

Main Results:

• Demonstrated stance-phase knee flexion in a person with an amputation using the 4BSF.
• Achieved a maximum knee flexion angle exceeding 10° during the stance phase.
• When paired with a SACH foot, the 4BSF reduced time to foot flat and doubled foot flat duration compared to conventional knees.

Conclusions:

• The novel 4BSF design successfully enables stance-phase knee flexion in amputees.
• This innovation offers potential for more natural and stable gait for individuals using prosthetic devices.
• Further research and larger studies are warranted to confirm these findings.