title: The influence of quadriceps strength asymmetry on patient-reported function at time of return to sport after anterior cruciate ligament reconstruction.
abstract: BACKGROUND
  An objective assessment of quadriceps strength after anterior cruciate ligament reconstruction (ACLR) is an important clinical measure to determine readiness to return to sport (RTS). Not all clinicians are equipped with the means to objectively quantify quadriceps strength limb symmetry indices (Q-LSIs) via lower extremity isokinetic dynamometers, as recommended by previous studies.
  
  
  OBJECTIVE
  The purpose of this study was to determine whether the International Knee Documentation Committee 2000 Subjective Knee Form (IKDC) score at time of RTS was a predictor of quadriceps strength in a young, athletic population after ACLR. Two hypotheses were tested: (1) Individuals with higher self-reports of function would demonstrate better quadriceps strength of the involved limb than individuals with lower self-reports of function at the time of RTS, and (2) individuals with higher self-reports of function would have normal quadriceps strength limb symmetry.
  
  
  METHODS
  Cohort study (diagnosis); Level of evidence, 2.
  
  
  METHODS
  At time of RTS, 139 subjects who had undergone ACLR completed the IKDC. In addition, an isometric quadriceps strength test (Biodex dynamometer) was performed on both lower extremities. Peak torques were calculated, as was the Q-LSI, determined by the formula (involved limb peak torque/uninvolved limb peak torque) × 100%. Participants were dichotomized based on IKDC scores: high IKDC (IKDC ≥90) and low IKDC (IKDC <90). Two-way analysis of variance was used to determine the effect of limb (involved vs uninvolved) and group (high vs low IKDC) on isometric quadriceps strength. Chi-square and logistic regression analyses were then performed to determine whether IKDC scores could predict Q-LSI.
  
  
  RESULTS
  At time of RTS, a significant correlation between IKDC scores and (1) peak isometric torque (r = 0.282, P < .001) and (2) Q-LSI (r = 0.357, P < .001) was observed. Individuals with IKDC scores ≥90 were 3 times (OR = 3.4; 95% CI, 1.71-6.93) more likely to demonstrate higher Q-LSI (≥90%). An IKDC score ≥94.8 predicted Q-LSI ≥90% with high sensitivity (0.813) and moderate specificity (0.493).
  
  
  CONCLUSIONS
  Participants with higher IKDC scores demonstrated an increased likelihood of presenting with greater involved limb quadriceps strength and better Q-LSI. Based on the results of this study, a patient-reported outcome measure, such as the IKDC, may be able to serve as a valuable screening tool for the identification of quadriceps strength deficits in this population; however, it should not be considered an accurate surrogate for isokinetic dynamometry. Furthermore, a score of ≥94.8 on the IKDC is likely to indicate that a patient's quadriceps strength is at an acceptable RTS level.
authors.affiliation: Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Division of Occupational Therapy and Physical Therapy, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA christin.zwolski@cchmc.org.
authors.forename: Christin
authors.initials: C
authors.lastname: Zwolski
authors.affiliation: Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Division of Occupational Therapy and Physical Therapy, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Division of Physical Therapy, School of Health and Rehabilitation Sciences, Ohio State University, Columbus, Ohio, USA.
authors.forename: Laura C
authors.initials: LC
authors.lastname: Schmitt
authors.affiliation: Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Division of Occupational Therapy and Physical Therapy, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, Ohio, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Quatman-Yates
authors.affiliation: Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.
authors.forename: Staci
authors.initials: S
authors.lastname: Thomas
authors.affiliation: Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, Ohio, USA Department of Orthopaedic Surgery, College of Medicine, University of Cincinnati, Cincinnati, Ohio, USA Departments of Biomedical Engineering and Rehabilitation Sciences, the Ohio State University, Columbus, Ohio, USA.
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Hewett
authors.affiliation: Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Division of Occupational Therapy and Physical Therapy, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, Ohio, USA.
authors.forename: Mark V
authors.initials: MV
authors.lastname: Paterno
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000502:physiology / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods; D001265:Athletic Injuries / Q000503:physiopathology / Q000601:surgery; D002648:Child; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology / Q000601:surgery; D007719:Knee Joint / Q000502:physiology / Q000601:surgery; D008137:Longitudinal Studies; D035002:Lower Extremity / Q000502:physiology; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*; D000068958:Return to Sport / Q000502:physiology*; D057566:Self Report; D019415:Torque; D055815:Young Adult
keywords: ACL reconstruction; IKDC; patient-reported outcomes; quadriceps strength; return to sport