Changes in motor unit activity associated with early recovery of muscle strength after knee arthroplasty

Abstract

Purpose: The purpose of this study was to investigate changes in motor unit activity associated with early recovery of muscle strength after knee arthroplasty. [Subjects] The subjects were eleven patients who received unicompartmental knee arthroplasty. [Methods] The maximum strength of isometric knee extension and surface electromyographic activity of the right vastus lateralis were measured before and after the operation and until discharge. Average integrated electromyographic activity at maximum isometric knee extension and mean power frequency calculated by fast Fourier transform were normalized by the values at five days after the operation. [Results]The strength of maximum isometric knee extension decreased immediately after the operation and then gradually recovered. Mean power frequency decreased significantly after the operation. [Conclusion] The results suggest that synchronization is an important factor for recovery of the strength of isometric knee extension in the early postoperative period.