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Individuals With Total Knee Arthroplasty Demonstrate Altered Anticipatory Postural Adjustments Compared With Healthy Control Subjects

Venema, Dawn M. PT, PhD1; Karst, Gregory M. PT, PhD1,2

Journal of Geriatric Physical Therapy: April/June 2012 - Volume 35 - Issue 2 - p 62–71
doi: 10.1519/JPT.0b013e3182353ee4
Research Reports

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.

Purpose: 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.

Discussion and 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.

1Division of Physical Therapy Education, University of Nebraska Medical Center, Omaha.

2School of Allied Health Professions, University of Nebraska Medical Center, Omaha.

Address correspondence to: Dawn M. Venema, PT, PhD, Division of Physical Therapy Education, University of Nebraska Medical Center, Omaha, NE 68198-4420 (

This study was financially supported by the George Blanton Research Grant Program of the Nebraska Foundation for Physical Therapy.

Previous dissemination of this study: Portions of these data were presented as a scientific poster at Physical Therapy 2008: The Annual Conference and Exposition of the American Physical Therapy Association, San Antonio, TX, June 11–14, 2008.

The authors disclose no conflicts of interest.

Copyright © 2012 the Section on Geriatrics of the American Physical Therapy Association
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