Total knee arthroplasty improves energy conversion efficiency during walking in patients with knee osteoarthritis

Energy conversion efficiency of human gait can be evaluated by calculating the ratio of conversion of mechanical energy from vertical motion to horizontal motion of the center of gravity through the movement of the joints. Osteoarthritis (OA) of the knee joint impairs this energy conversion efficiency. Total knee arthroplasty is the standard treatment for knee OA. However, its effect on energy conversion efficiency is unclear. In this study, we investigated how energy conversion efficiency changed in the gait of patients with knee OA before and after surgery. Twelve patients with unilateral knee OA who underwent total knee arthroplasty were included. Ground walking was measured using a motion capture system (VICON®) before and 6 months after surgery. We calculated potential and kinetic energy from the coordinate change of the center of mass to obtain energy conversion efficiency. Other gait parameters such as gait speed, vertical movement distance of the body center, step length, hip joint angle, and trailing and leading limb angles were assessed. Energy conversion efficiency on the operated side significantly improved from 41.4 ± 12.2% to 57.5 ± 9.2% 6 months after surgery. Other gait parameters on the operated side were significantly improved after surgery compared with before surgery. Step length on the operated and the non-operated sides and trailing limb angles on the non-operated side before surgery correlated to energy conversion efficiency, while at 6 months after surgery, gait speed and step length on the non-operated side correlated to energy conversion efficiency. Energy conversion efficiency was strongly improved postoperatively in patients with knee OA.