title: Persistent neuromuscular and corticomotor quadriceps asymmetry after anterior cruciate ligament reconstruction.
abstract: BACKGROUND
  Return to activity in the presence of quadriceps dysfunction may predispose individuals with anterior cruciate ligament reconstruction (ACLR) to long-term joint degeneration. Asymmetry may manifest during movement and result in altered knee-joint-loading patterns; however, the underlying neurophysiologic mechanisms remain unclear.
  
  
  OBJECTIVE
  To compare limb symmetry of quadriceps neuromuscular function between participants with ACLR and participants serving as healthy controls.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Research laboratory.
  
  
  METHODS
  A total of 22 individuals with ACLR (12 men, 10 women) and 24 individuals serving as healthy controls (12 men, 12 women).
  
  
  METHODS
  Normalized knee-extension maximal voluntary isometric contraction (MVIC) torque (Nm/kg), quadriceps central activation ratio (CAR) (%), quadriceps motor-neuron-pool excitability (Hoffmann reflex to motor wave ratio), and quadriceps active motor threshold (AMT) (% 2.0 T) were measured bilaterally and used to calculate limb symmetry indices for comparison between groups. We used analyses of variance to compare quadriceps Hoffmann reflex to motor wave ratio, normalized knee-extension MVIC torque, quadriceps CAR, and quadriceps AMT between groups and limbs.
  
  
  RESULTS
  The ACLR group exhibited greater asymmetry in knee-extension MVIC torque (ACLR group = 0.85 ± 0.21, healthy group = 0.97 ± 0.14; t44 = 2.26, P = .03), quadriceps CAR (ACLR group = 0.94 ± 0.11, healthy group = 1.00 ± 0.08; t44 = 2.22, P = .04), and quadriceps AMT (ACLR group = 1.13 ± 0.18, healthy group = 1.02 ± 0.11; t34 = -2.46, P = .04) than the healthy control group.
  
  
  CONCLUSIONS
  Asymmetries in measures of quadriceps function and cortical excitability were present in patients with ACLR. Asymmetry in quadriceps strength, activation, and cortical excitability persisted in individuals with ACLR beyond return to recreational activity. Measuring the magnitude of asymmetry after ACLR represents an important step in understanding long-term reductions in self-reported function and increased rate of subsequent joint injury in otherwise healthy, active individuals after ACLR.
authors.affiliation: Department of Kinesiology and Sport Sciences, University of Miami, Coral Gables, FL; Departments of.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Kuenze
authors.forename: Jay
authors.initials: J
authors.lastname: Hertel
authors.forename: Arthur
authors.initials: A
authors.lastname: Weltman
authors.forename: David
authors.initials: D
authors.lastname: Diduch
authors.forename: Susan A
authors.initials: SA
authors.lastname: Saliba
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Hart
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000009:adverse effects* / Q000379:methods; D001265:Athletic Injuries / Q000150:complications*; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D007719:Knee Joint / Q000473:pathology / Q000503:physiopathology; D008297:Male; D018908:Muscle Weakness / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology; D011183:Postoperative Complications / Q000175:diagnosis / Q000503:physiopathology; D011597:Psychomotor Performance; D052097:Quadriceps Muscle / Q000473:pathology / Q000503:physiopathology; D019415:Torque
keywords: limb symmetry index; quadriceps activation; transcranial magnetic stimulation