title: Clinically-relevant measures associated with altered contact forces in patients with anterior cruciate ligament deficiency.
abstract: BACKGROUND
  Knee joint contact forces are altered after anterior cruciate ligament injury during walking and may be related to clinically-relevant measures of impairments or self-reported function. The purpose of this study was to investigate the association of several clinically-relevant measures with altered knee contact forces in patients with anterior cruciate ligament injury.
  
  
  METHODS
  Data for this study represent a cross-sectional observational analysis of thirty-seven (23 M, 14 F) patients with complete unilateral anterior cruciate ligament injury. Gait analysis with electromyography was used to obtain estimates of tibiofemoral joint contact force using an electromyography-driven musculoskeletal model. Multivariable linear regression was used to identify measures associated with tibiofemoral joint contact force.
  
  
  RESULTS
  Involved knee extensor muscle strength and patient-reported knee function on the Global Rating Scale of perceived function were significantly associated with peak tibiofemoral contact force for the involved limb. Patients who were stronger and who perceived higher knee function walked with greater contact forces on their involved knees. After controlling for walking speed, involved extensor strength explained 8.9% of the variance in involved peak tibiofemoral contact force and score on the Global Rating Scale explained an additional 9.4% of the variance.
  
  
  CONCLUSIONS
  Improvements in involved quadriceps strength and overall function as measured by patient self-report may be important for increasing involved limb contact forces, thereby restoring loading symmetry in these patients who demonstrate decreased involved limb loading after injury. These results highlight the potential value of studying the recovery of strength, self-reported function and joint loading symmetry in patients with anterior cruciate ligament injury.
authors.affiliation: School of Kinesiology, University of Michigan, Ann Arbor, MI, USA. Electronic address: egardin@umich.edu.
authors.forename: Emily S
authors.initials: ES
authors.lastname: Gardinier
authors.affiliation: Delaware Rehabilitation Institute, University of Delaware, Newark, DE, USA; Department of Mechanical Engineering, University of Delaware, Newark, DE, USA.
authors.forename: Kurt
authors.initials: K
authors.lastname: Manal
authors.affiliation: Delaware Rehabilitation Institute, University of Delaware, Newark, DE, USA; Department of Mechanical Engineering, University of Delaware, Newark, DE, USA.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Buchanan
authors.affiliation: Delaware Rehabilitation Institute, University of Delaware, Newark, DE, USA; Department of Physical Therapy, University of Delaware, Newark, DE, USA.
authors.forename: Lynn
authors.initials: L
authors.lastname: Snyder-Mackler
mesh_terms: D000328:Adult; D000368:Aged; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena / Q000502:physiology; D003430:Cross-Sectional Studies; D004576:Electromyography; D005260:Female; D005269:Femur; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D016014:Linear Models; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D052097:Quadriceps Muscle / Q000503:physiopathology*; D013977:Tibia; D016138:Walking / Q000502:physiology
keywords: ACL injury; Contact force; Patient-reported function; Quadriceps strength
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