Individuals with total knee arthroplasty demonstrate altered anticipatory postural adjustments compared with healthy control subjects.
BACKGROUND
Persons with total knee arthroplasty (TKA) have many impairments that may compromise postural control. Most work examining postural control following TKA has focused on static and reactive postural control.


OBJECTIVE
The purpose of this study was to (1) compare anticipatory postural adjustments (APAs) between individuals with TKA and healthy controls; and (2) identify possible pre- to postoperative changes in APAs in those undergoing TKA.


METHODS
Ten individuals planning TKA and 10 healthy age- and sex-matched controls were recruited. During a standing reaching task, lower extremity muscle activity was measured using electromyography (EMG) onsets and normalized EMG amplitudes, and center of pressure (COP) excursion was measured via a force platform. Other outcome measures included isometric strength of the knee flexors and extensors. Individuals in the TKA group were tested preoperatively, and at 3 and 6 months postoperatively. Controls were also measured 3 times over 6 months.


RESULTS
There were no pre- to postoperative differences in lower extremity EMG onsets, normalized EMG amplitudes, or COP excursion in those with TKA. When compared to controls, individuals with TKA demonstrated lower EMG amplitudes of the vastus lateralis and biceps femoris, whereas EMG onsets and COP excursion did not differ. Individuals with TKA demonstrated lower knee extension torque.


CONCLUSIONS
It seems that the surgery itself did not alter APAs among individuals with TKA. Potential contributors to the differences in EMG amplitudes in those with TKA compared to controls, such as impaired neural activation or efforts to reduce stress on the involved knee joint, need further investigation.
Division of Physical Therapy Education, University of Nebraska Medical Center, Omaha, NE 68198-4420, USA. dvenema@unmc.edu
Dawn M
DM
Venema
Gregory M
GM
Karst
D000054:Acceleration; D000368:Aged; D059031:Anticipation, Psychological; D019645:Arthroplasty, Replacement, Knee / Q000523:psychology / Q000534:rehabilitation*; D004576:Electromyography / Q000379:methods; D015444:Exercise; D005260:Female; D006801:Humans; D035002:Lower Extremity / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D009046:Motor Neurons / Q000502:physiology; D020370:Osteoarthritis, Knee / Q000523:psychology / Q000534:rehabilitation / Q000601:surgery; D011184:Postoperative Period; D004856:Postural Balance / Q000502:physiology*; D057234:Preoperative Period; D011312:Pressure; D011597:Psychomotor Performance / Q000502:physiology*; D011859:Radiography; D013996:Time and Motion Studies