Quadriceps femoris function during knee extension following total knee arthroplasty

Electromyographic signals (EMG) from surface electrodes over the vastus medialis, rectus femoris and vastus lateralis were monitored during isometric knee extension for 10 TKA patients and 6 control subjects. No significant side-to-side differences in normalized EMG signals from any of the monitored muscles were found when the left and right legs of the control group were compared or when the operative and the non-operative legs of the patient group were compared. However, both the operative and the non-operative legs in the patient group differed significantly (p < 0.01) in normalized EMG from the control group. This study has shown that a muscle imbalance, possibly leading to patellar tracking problems, does not routinely exist following TKA through a medial parapatellar incision.