Muscle activation pattern and gait biomechanics after total knee replacement.

The aim of this study is to evaluate residual muscle function abnormalities after total knee replacement, with respect to gait kinematics and kinetics.Longitudinal study on a follow-up of up to two years.Gait usually presents an excellent improvement after total knee replacement. Nevertheless, some kinematics and kinetics abnormalities persist even after a long period of time and they might have implications in long-term prosthesis failure. Additionally, lower limb muscle activity has not been sufficiently studied in the past directly by means of dynamic EMG.Nine patients who had a posterior cruciate sparing total knee replacement design were evaluated by means of clinical assessment and gait analysis at the end of rehabilitation trials at six, twelve and twenty four months. EMG from trunk and lower limb muscles was registered and elaborated through a statistical detector for the on-off timing.Gait analysis showed a slow gait, with a "stiff knee gait pattern" and prolonged muscular co-contractions during stance.Knee kinematics and kinetics abnormalities during loading acceptance after total knee replacement are associated with co-contractions in muscular activation pattern.Gait pattern at two years after total knee replacement is deemed unphysiological, potentially dangerous for the implant duration in time and responsible for residual disability in patients. Muscular behavior during daily activities provides insight into the integration of the prosthetic biomechanics within the muscular-skeletal system. This information is of relevance to improve prosthetic design, rehabilitation programs and knee motor performance