Study: ‘Auto-locking’ prosthetic knee joint more efficient than weight-activated brake joint

BOSTON — There are functional and biomechanical differences between weight-activated brake and automatic stance-phase lock prosthetic knee joint mechanisms, according to data presented here at the American Orthotic and Prosthetic Association National Assembly.

“Our goal was to examine the differences in gait patterns between knees, the differences in functional measures – such as walking speed and efficiency – and the associations between differences in gait patterns and functional measures,” Jan Andrysek, PEng, PhD, said.

Jan Andrysek

According to Andrysek, the AutoLock All-Terrain Knee, a system containing a lock that automatically engages and disengages in response to loads placed on the user’s limb, showed effective results. The knee locks when a flexion moment is produced at the lock control axis, he said.

Researchers conducted a study of 10 unilateral transfemoral amputees. Each previously used weight-activated brake (WAB) knees. The study investigated results of a timed walk test for walking speed, physiologic cost index during a 6-minute walk test for energy expenditure and a kinematic and kinetic gait analysis.

Researchers found the AutoLock system improved stability vs. polycentric knees and improved gait speed vs. WAB knees.

“We also saw greater pelvic tilt, range of motion and interior tilt, patient-perceived improved stability, improved energy expenditure, easier initiation of swing phase flexion and improved gait patterns retraining due to loading requirements,” he said.

The researchers plan to continue their work and conduct a clinical comparative study with other high-end knee joints, according to Andrysek. – by Shawn M. Carter


Andrysek, J. Functional and biomechanical differences between weight-activated brake (WAB) and autolock prosthetic knee joint mechanisms. Presented at: American Orthotic and Prosthetic Association National Assembly; Sept. 8-11, 2016; Boston.

Disclosure: Andrysek reports he is a member of the Holland Bloorview Kids Rehabilitation Hospital.


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