A study that compared the effects of a conventional prosthetic knee with a microprocessor-controlled knee (MPK) on stair ascent strategies found that people with a transfemoral amputations were more likely to use a step-over-step strategy while using an MPK than when using a conventional prosthesis.
The researchers compared self-selected stair ascent strategies among 14 participants using conventional knees or the Ottobock X2 knee. Ten people without an amputation also completed a stair ascent session wherein lower-limb joint angles, moment, and powers and ground reaction forces were calculated. The research team also examined between-limb differences, differentiated stair ascent mechanics between the MPK users and the able-bodied group, and determined which factors were associated with differences in knee position during initial contact and swing among the MPK users. The study was published in the October issue of Clinical Orthopaedics and Related Research.
One participant self-selected a step-over-step strategy while using a conventional knee, while ten individuals chose a step-over-step strategy while using the MPK. According to the researchers, the participants used greater prosthetic knee flexion during initial contact and swing while using the MPK compared to conventional knees. This increased prosthetic knee flexion made the knee kinematics similar to the able-bodied group during swing but not during initial contact. Prosthetic knee flexion during initial contact and swing correlated to hip power during pull-up and push-up/early swing, and the increased prosthetic knee flexion from the MPK placed large power demands on the user’s hip during pull-up and push-up/early swing. The study’s authors suggested that a modified strategy that uses less knee flexion can be used to allow step-over-step ascent in individuals with less hip strength.