The University of California Biomechanics Laboratory four-bar polycentric knee linkage. A clinical trial in 20 active above-knee amputees.

A four-bar polycentric prosthetic knee linkage developed by the University of California Biomechanics Laboratory (UCBL) was tested clinically in 20 active veteran above-knee amputees. The mean follow-up period was 12.3 months. At final follow-up evaluation, positive subjective responses were reported by 80% of the amputees. More than one-third reported that the device was superior to any that they had used previously. Almost all subjects found that prior levels of daily activity and the ability to perform specific activities were maintained or enhanced. The increase in knee flexion afforded by the mechanism was found to be an advantage. There was no significant change in various fundamental gait parameters. Problems caused by excessive wear of anodized aluminum linkage pins and by air leaks in the pneumatic swing-phase control unit were corrected easily. These preliminary results encourage further clinical application and study of the UCBL four-bar polycentric knee.