title: Quadriceps and hamstrings muscle dysfunction after total knee arthroplasty.
abstract: BACKGROUND
  Although TKA reliably reduces pain from knee osteoarthritis, full recovery of muscle strength and physical function to normal levels is rare. We presumed that a better understanding of acute changes in hamstrings and quadriceps muscle performance would allow us to enhance early rehabilitation after TKA and improve long-term function.
  
  
  OBJECTIVE
  The purposes of this study were to (1) evaluate postoperative quadriceps and hamstrings muscle strength loss after TKA and subsequent recovery using the nonoperative legs and healthy control legs for comparison, and (2) measure hamstrings coactivation before and after TKA during a maximal isometric quadriceps muscle contraction and compare with nonoperative and healthy control legs.
  
  
  METHODS
  We prospectively followed 30 patients undergoing TKA at 2 weeks preoperatively and 1, 3, and 6 months postoperatively and compared patient outcomes with a cross-sectional cohort of 15 healthy older adults. Bilateral, isometric strength of the quadriceps and hamstrings was assessed along with EMG measures of hamstrings coactivation during a maximal isometric quadriceps contraction.
  
  
  RESULTS
  There were no differences in strength loss or recovery between the quadriceps and hamstrings muscles of the operative leg throughout the followup, although differences existed when compared with nonoperative and healthy control legs. Hamstrings muscle coactivation in the operative leg during a maximal quadriceps effort was elevated at 1 month (144.5%) compared to the nonoperative leg.
  
  
  CONCLUSIONS
  Although quadriceps dysfunction after TKA typically is recognized and addressed in postoperative therapy protocols, hamstrings dysfunction also is present and should be addressed.
  
  
  CONCLUSIONS
  Quadriceps and hamstrings muscle strengthening should be the focus of future rehabilitation programs to optimize muscle function and long-term outcomes.
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of Colorado Denver, Aurora, CO 80045, USA.
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Stevens-Lapsley
authors.forename: Jaclyn E
authors.initials: JE
authors.lastname: Balter
authors.forename: Wendy M
authors.initials: WM
authors.lastname: Kohrt
authors.forename: Donald G
authors.initials: DG
authors.lastname: Eckhoff
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000534:rehabilitation / Q000601:surgery*; D011446:Prospective Studies; D052097:Quadriceps Muscle / Q000503:physiopathology*; D020127:Recovery of Function; D013997:Time Factors; D016896:Treatment Outcome