title: Knee-Extension Torque Variability and Subjective Knee Function in Patients with a History of Anterior Cruciate Ligament Reconstruction.
abstract: BACKGROUND
  When returning to physical activity, patients with a history of anterior cruciate ligament reconstruction (ACL-R) often experience limitations in knee-joint function that may be due to chronic impairments in quadriceps motor control. Assessment of knee-extension torque variability may demonstrate underlying impairments in quadriceps motor control in patients with a history of ACL-R.
  
  
  OBJECTIVE
  To identify differences in maximal isometric knee-extension torque variability between knees that have undergone ACL-R and healthy knees and to determine the relationship between knee-extension torque variability and self-reported knee function in patients with a history of ACL-R.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Laboratory.
  
  
  METHODS
  A total of 53 individuals with primary, unilateral ACL-R (age = 23.4 ± 4.9 years, height = 1.7 ± 0.1 m, mass = 74.6 ± 14.8 kg) and 50 individuals with no history of substantial lower extremity injury or surgery who served as controls (age = 23.3 ± 4.4 years, height = 1.7 ± 0.1 m, mass = 67.4 ± 13.2 kg).
  
  
  METHODS
  Torque variability, strength, and central activation ratio (CAR) were calculated from 3-second maximal knee-extension contraction trials (90° of flexion) with a superimposed electrical stimulus. All participants completed the International Knee Documentation Committee (IKDC) Subjective Knee Evaluation Form, and we determined the number of months after surgery. Group differences were assessed using independent-samples t tests. Correlation coefficients were calculated among torque variability, strength, CAR, months after surgery, and IKDC scores. Torque variability, strength, CAR, and months after surgery were regressed on IKDC scores using stepwise, multiple linear regression.
  
  
  RESULTS
  Torque variability was greater and strength, CAR, and IKDC scores were lower in the ACL-R group than in the control group (P < .05). Torque variability and strength were correlated with IKDC scores (P < .05). Torque variability, strength, and CAR were correlated with each other (P < .05). Torque variability alone accounted for 14.3% of the variance in IKDC scores. The combination of torque variability and number of months after surgery accounted for 21% of the variance in IKDC scores. Strength and CAR were excluded from the regression model.
  
  
  CONCLUSIONS
  Knee-extension torque variability was moderately associated with IKDC scores in patients with a history of ACL-R. Torque variability combined with months after surgery predicted 21% of the variance in IKDC scores in these patients.
authors.affiliation: Departments of * Kinesiology and.
authors.forename: John
authors.initials: J
authors.lastname: Goetschius
authors.affiliation: Departments of * Kinesiology and.|Orthopaedics, University of Virginia, Charlottesville.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Hart
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000502:physiology; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D001265:Athletic Injuries / Q000503:physiopathology; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D052097:Quadriceps Muscle / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology*; D011998:Recreation; D000068958:Return to Sport / Q000502:physiology; D057566:Self Report; D019415:Torque; D055815:Young Adult
keywords: disability; motor control; neuromuscular; quadriceps muscle