title: The effect of insufficient quadriceps strength on gait after anterior cruciate ligament reconstruction.
abstract: OBJECTIVE
  To determine the effect of quadriceps strength and joint stability on gait patterns after anterior cruciate ligament injury and reconstruction.
  
  
  METHODS
  Cross-sectional comparative study in which four groups underwent motion analysis with surface electromyography.
  
  
  BACKGROUND
  Individuals following anterior cruciate ligament rupture often demonstrate reduced knee angles and moments during the early stance phase of gait. Alterations in gait can neither be ascribed to instability nor to quadriceps weakness alone when both are present.
  
  
  METHODS
  Twenty-eight individuals with complete anterior cruciate ligament rupture (10 patients with acute rupture, 8 patients following reconstruction with quadriceps strength >90% of the uninvolved side [strong-anterior cruciate ligament reconstructed group], and 10 patients after reconstruction with quadriceps strength <80% of the uninvolved side [weak-anterior cruciate ligament reconstructed group]), and 10 uninjured subjects underwent an examination of their lower extremity to collect kinematics, kinetics, and electromyography during walking and jogging. Anterior cruciate ligament reconstruction was arthroscopically assisted and a double loop semitendinosis-gracilis autograft or allograft was used as a graft source. All reconstructed subjects had stable knees, full range of motion, and no effusion or pain at the time of testing (more than three months after surgery).
  
  
  RESULTS
  Knee angles and moments of the strong group were indistinguishable from the uninjured group during early stance of both walking and jogging. The weak subjects had reduced knee angles and moments during walking, and jogged similarly to the deficient subjects. Regression analysis revealed a significant effect between early stance phase knee angles and moments and quadriceps strength during both walking and jogging.
  
  
  CONCLUSIONS
  Inadequate quadriceps strength contributes to altered gait patterns following anterior cruciate ligament reconstruction.
  
  
  CONCLUSIONS
  Rapid strengthening following anterior cruciate ligament injury or reconstruction may contribute to a safe return to high-level activities.
authors.affiliation: Department of Physical Therapy, 301 McKinly Lab, University of Delaware, Newark, DE 19716, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Lewek
authors.forename: Katherine
authors.initials: K
authors.lastname: Rudolph
authors.forename: Michael
authors.initials: M
authors.lastname: Axe
authors.forename: Lynn
authors.initials: L
authors.lastname: Snyder-Mackler
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D016059:Range of Motion, Articular; D014741:Video Recording